Provided is an ICP mass spectrometer which is able to effectively discharge residual water by limiting the consumption of Ar gas and a fluctuation in supply pressure of an Ar gas source at the time of an Ar gas purge for a coolant system. The ICP mass spectrometer is provided with: a device body part 1; a coolant system 2 that supplies a coolant from a water source 20 to to-be-cooled structure parts including a high-frequency power supply 12, a high-frequency coil 18, and a sample introduction part 13, which need to be cooled; and an Ar gas supply system 3. Intermediate valves V2, V3 are disposed on the downstream side of a main valve V0, a purge gas channel 32 having a purge valve V1, and a meeting point G of the purge gas channel 32. The to-be-cooled structure parts are connected to a cooling-use pipe on the downstream side of the intermediate valves V2, V3. A valve control part 35 is configured to perform intermittent purge control of repeating accumulation and discharge of the Ar gas on the upstream side of the intermediate valves V2, V3 by intermediately opening and closing the intermediate valves V2, V3 when the Ar gas is being sent.