diff --git a/backend/app/controllers/post_imports_controller.rb b/backend/app/controllers/post_imports_controller.rb
index daa6786..1d8abe6 100644
--- a/backend/app/controllers/post_imports_controller.rb
+++ b/backend/app/controllers/post_imports_controller.rb
@@ -78,7 +78,7 @@ class PostImportsController < ApplicationController
     rows = Array(params[:rows])
     raise ArgumentError, '取込件数が多すぎます．' if rows.length > PostImportSourceParser::MAX_ROWS
 
-    rows.map do |row|
+    normalised_rows = rows.map do |row|
       value = ActionController::Parameters.new(row).permit(:source_row, :sourceRow, :url, :metadata_url, :metadataUrl,
                                                             attributes: {}, provenance: {}, tag_sources: {},
                                                             fetch_warnings: [], validation_warnings: [])
@@ -109,5 +109,12 @@ class PostImportsController < ApplicationController
 
       normalised.symbolize_keys
     end
+    source_rows = normalised_rows.map { _1[:source_row] }
+    if source_rows.any? { |value| Integer(value, exception: false).to_i <= 0 } ||
+       source_rows.uniq.length != source_rows.length
+      raise ArgumentError, '元行番号が不正です．'
+    end
+
+    normalised_rows
   end
 end
diff --git a/backend/app/services/post_import_previewer.rb b/backend/app/services/post_import_previewer.rb
index 0cd77ea..307c243 100644
--- a/backend/app/services/post_import_previewer.rb
+++ b/backend/app/services/post_import_previewer.rb
@@ -47,10 +47,9 @@ class PostImportPreviewer
         attributes[field] = value
         provenance[field] = 'automatic'
       end
-      post = Post.new(url:)
-      post.valid?
-      normal_url = post.url
-      errors = post.errors.to_hash.transform_values(&:dup)
+      normal_url = normalised_url(url)
+      errors = { }
+      errors[:url] = ['URL が不正です．'] if normal_url.blank?
       validation_warnings = []
       errors[:url] = ['URL が重複しています．'] if normal_url.present? && urls.key?(normal_url)
       urls[normal_url] = true if normal_url.present?
@@ -165,6 +164,7 @@ class PostImportPreviewer
                     video_ms: parse_duration(attributes['duration'], errors))
     post.valid?
     post.errors.each { |error| (errors[error.attribute] ||= []) << error.message }
+    errors.delete(:url)
   end
 
   def parse_duration value, errors
diff --git a/backend/app/services/post_import_runner.rb b/backend/app/services/post_import_runner.rb
index b2de331..2b20dff 100644
--- a/backend/app/services/post_import_runner.rb
+++ b/backend/app/services/post_import_runner.rb
@@ -11,7 +11,11 @@ class PostImportRunner
     raise ArgumentError, "取込件数は #{ MAX_ROWS } 件までです．" if @rows.length > MAX_ROWS
     raise ArgumentError, '取込データが大きすぎます．' if @rows.sum { |row| row.to_json.bytesize } > PostImportSourceParser::MAX_BYTES
 
-    results = @rows.map { |row| run_row(normalise_row(row)) }
+    normalised_rows = @rows.map { |row| normalise_row(row) }
+    source_rows = normalised_rows.map { _1['source_row'] }
+    raise ArgumentError, '元行番号が重複しています．' if source_rows.uniq.length != source_rows.length
+
+    results = normalised_rows.map { |row| run_row(row) }
     { created: results.count { _1[:status] == 'created' }, skipped: results.count { _1[:status] == 'skipped' },
       failed: results.count { _1[:status] == 'failed' }, rows: results }
   end
@@ -77,6 +81,8 @@ class PostImportRunner
     raise ArgumentError unless metadata_url.nil? || metadata_url.is_a?(String)
     raise ArgumentError if metadata_url.to_s.bytesize > PostImportSourceParser::MAX_CELL_BYTES
     raise ArgumentError if row.to_json.bytesize > PostImportSourceParser::MAX_BYTES
+    tag_sources = row['tag_sources']
+    raise ArgumentError unless tag_sources.nil? || tag_sources.is_a?(Hash)
   end
 
   def normalise_row row