A pressure control valve piezoelectric element driving circuit is provided for a pressure type flow rate control device provided with a flow rate self-diagnosis function for comparing initial pressure drop characteristics data measured and with pressure drop characteristics data in a flow rate diagnosis which are measured under conditions that are the same for both measurements to detect malfunction in flow rate control from a difference between both characteristics data, wherein a first discharge circuit slowly discharges a piezoelectric element driving voltage applied to the piezoelectric element according to a step-down command signal from a CPU, through a step-down command circuit to step down the voltage, and a second discharge circuit that rapidly discharges a piezoelectric element driving voltage applied to the piezoelectric element according to a high-speed step-down command signal from the CPU, through a high-speed step-down command circuit to step down the voltage.