An apparatus that identifies the type of a test cell based on a result obtained by performing mass spectrometry on the test cell includes a higher-level database, which contains mass lists that each list ion mass values of constituent components of a known cell, and a lower-level database, which contains partial mass lists that each list only strain-specific ion mass values out of the ion mass values. The higher-level database is first searched for a test mass list which is created from the result of the mass spectrometry performed on the test cell, and based on a result of the search, an organism species to be searched in the following search operation is determined. Mass values common to the organism species are subsequently deleted from the mass list for the test cell, and the mass list having undergone the deletion operation is used to search the lower-level database.