A mass spectrometer and a mass spectrometry method adapted for mass spectrometry of a hardly volatile minuscule organic foreign matter of several μm often causing a device defect are disclosed. A sample gasified by a sample heating probe is introduced into an ion source, and the sample thus ionized is detected by being separated in accordance with the mass-to-charge ratio. In this mass spectrometry technique, the sample heating probe is covered with a cylindrical gas guide mechanism, and the gasified sample is led efficiently to the ion source by the gas guide mechanism, thereby making possible the contribution by the sample components which otherwise might be dispersed and wasted in the prior art. As a result, the mass spectrometry with higher sensitivity and S/N than in the prior art is realized.