An investigation apparatus according to an embodiment includes a processor that executes a process including: analyzing uniqueness of a plurality of values included in an attribute for each attribute of a table; reducing a plurality of values included in an attribute of which the analyzed uniqueness is lower than a predetermined value by a predetermined ratio with respect to an investigation original table and outputting a feature of the investigation original table; reducing a plurality of values included in an attribute of which the analyzed uniqueness is higher than a predetermined value by a predetermined ratio with respect to an investigation target table and outputting a feature of the investigation target table; and investigating similarity of the investigation target table to the investigation original table by comparing the feature of the investigation original table with the feature of the investigation target table.