The invention relates to the field of supercritical fluid chromatography and provides a shunting device for combined use of a supercritical fluid chromatograph and a mass spectrometer. The shunting device is simple in structure and can effectively reduce the supercritical carbon dioxide vaporization phenomenon and improve the mass spectrum resolution and accuracy. The device comprises a reagent bottle, a back pressure pump, a first three-way control valve, a second three-way control valve and a stop valve, wherein one inlet end of the first three-way control valve is used for communicating with a sample flow-out pipeline of the chromatograph, and the other inlet end communicates with the reagent bottle through the back pressure pump; one outlet end of the first three-way control valve is connected with an inlet end of the second three-way control valve, the other inlet end of the second three-way control valve is used for being connected with a phase combining manager of the chromatograph, and an outlet end of the second three-way control valve communicates with a sample flow-in pipeline of the mass spectrometer; the stop valve is arranged at the inlet end, connected with the phase combining manager of the chromatograph, of the second three-way control valve and can detect pressure from two sides, and the stop valve is opened when pressure difference occurs.