PURPOSE: To provide a liquid chromatographic mass spectrograph requiring to replace ionization sections in response to various samples and capable of simply replacing the ionization sections without requiring the complex adjusting work.

CONSTITUTION: An interface section 30 arranged between a liquid chromatograph section 10 and a mass spectrograph section 20 is provided with multiple ionization sections 31, 34 for ionization by different methods, multiple inlets 35a, 33b connected to the ionization sections 31, 34, and a heating pipe 35 connecting the pipes from the inlets 35a, 33b in the middle and connecting them to the ion guide port of the mass spectrograph section 20. Both ionization sections 31, 34 can be used with no replacing work.