To precisely analyze an agrochemical and a volatile organic compound by one GC/MS, without carrying out troublesome column replacing work.

An inlet end of a first column 22 incorporated in a column oven 21 is connected to a head space sample introduction device 10, an inlet end of the second column 23 is connected to a sample vaporization chamber 15 of a liquid sample introduction device 14, and outlet side end parts 22a, 23a of the both columns 22, 23 are connected to an ionization chamber 42 arranged inside a vacuum chamber 41 via an interface part 30. Components of a sample are separated using either of a combination of the head space sample introduction device 10 and the the first column 22, or a combination of the liquid sample introduction device 14 and the second column 23, and sample gas is introduced directly into the ionization chamber 42 to execute mass spectrometry.