The present invention provides a laser irradiation mass spectrometer capable of analyzing components of living tissue or living cells with high accuracy. It includes a laser unit for irradiating a sample with a beam of laser light and controlling the irradiation spot of the laser beam on the sample; and a mass analyzer for performing a mass analysis of the ions generated at the irradiation spot, where the mass analyzer uses a frequency-driven ion trap and a time-of-flight mass spectrometer to carry out the mass analysis. The ion trap of this system assuredly traps ions having large mass to charge ratios, and enables the system to carry out analyses on samples of large molecules. Preferably, a digital driving method is used to drive the aforementioned frequency-driven ion trap. Also, a multi-turn time-of-flight mass spectrometer may preferably be used as the aforementioned time-of-flight mass spectrometer.