A mass spectrometer includes a position controller that adjusts a position of a sample plate, an image acquirer that acquires an image of a sample/matrix mixture on the sample plate, a laser light emitter that emits laser light to the sample/matrix mixture, a detector that detects ions generated from the sample/matrix mixture by the emission of the laser light by the laser light emitter, and a controller that acquires an image of a sample plate identification code displayed on the sample plate by utilizing the image acquirer and specifies plate identification information of the sample plate from the image of the sample plate identification code.