To provide a suck back valve system which eliminates the failure of a suck back function.

The suck back valve system includes: an integral suck back valve SV provided with a suck back function for preventing an on-off valve opening and closing by a first air pressure actuator from the liquid sagging by a diaphragm in cooperation with the closing action; and a protective on-off valve 3 provided to be adjacent to the upstream side as the countermeasures against the action defect of the integral suck back valve SV and opening and closing by a second air pressure actuator. The suck back valve system is also provided with an opening and closing control part for finishing the full close operation of the protective on-off valve 3 before the integral suck back valve SV is fully closed in the full close operation of the integral suck back valve SV.