1. An information extraction supporting apparatus, comprising: a computer system implemented in computer hardware and configured to implement computer instructions, the computer system 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; an extractor which extracts an expression belonging to the selected attribute from the document as an attribute expression, and when a second attribute for which an attribute expression is not extracted among third attributes required for the purpose of the analysis is present and when an attribute expression belonging to other third attributes commonly belongs to the second attribute, uses the attribute expression belonging to the other third attributes as an attribute expression of the second attribute; a second acquirer which acquires a correct or incorrect determination for the one or more attribute candidates; and a learning unit which executes learning based on the correct or incorrect determination.