1. An information extraction supporting apparatus, comprising: a first acquirer which acquires a document from which at least one attribute indicating a type of desired information is extracted as an analysis target; a determiner which determines whether or not the at least one attribute is valid, and obtains at least one of the valid attributes as one or more attribute candidates; a selector which selects an attribute to be used for an analysis from the one or more attribute candidates as a selected attribute; and an extractor which extracts an expression belonging to the selected attribute from the document as an attribute expression.