The mass spectrometer according to the present invention includes a light source for emitting pulse light including a plurality of wavelengths; an ionizer for ionizing molecules of a sample by irradiating the light from the light source to the sample; and a mass analyzer for separating ions ionized in the ionizer according to their mass to charge ratios. For the light source, one including a plurality of ultrashort pulse laser sources each emitting a wavelength different from others, and one emitting ultrashort pulse light including plural wavelengths ranging from the visible region to the infrared region generated by dispersing an ultrashort pulse light with continuous (white) spectrum can be used. Pulse lights having plural wavelengths ranging from near infrared to the ultraviolet region respectively share the role; i.e., one of them vaporizes the sample without fragmenting it, and another ionizes the vaporized sample with the single-photon process or two-photon (or multi-photon) process. This enables ionization of protein complexes as a whole contained in the sample, and enables mass analyses of them.