まんま require 'hpricot' xml = <<XML <entries> <entry> <name>c</name> <value>d</value> </entry> </entries> XML Hpricot::Builder.set :indent, 2 doc = Hpricot::XML(xml) doc.at('entry').before do tag!'entry' do tag!'name', 'a' tag!'value', 'b' end end puts doc で、 <entries> <entry><name>a</name><value>b</value></entry></entries>