To provide a mass/flow rate control unit for performing the examination operation of mass/flow rate by the unit itself, incorporating a tank for examination.

In the mass/flow rate control unit, a mass/flow rate detecting means 8 for outputting a flow rate signal by detecting the mass/flow rate of fluid flowing through a channel, and a flow rate control valve mechanism 10 for controlling the mass/flow rate, by changing a valve opening by a valve drive signal are interposed in the channel 6 for allowing fluid to flow. In the mass/flow rate control unit, a control means 18, for controlling the flow rate control valve mechanism, based on a flow rate setting signal inputted from the outside and the flow rate signal, is provided. In the channel, a valve section 42 for examination for opening/closing the channel, a tank section 44 for examination having prescribed capacity, and a pressure detection means 46 for outputting a pressure detection signal by detecting the pressure of the fluid are provided. The mass/flow rate control unit has an examination control means 48 for controlling so that mass/flow rate examination operation is conducted by using the valve for examination, the tank section for examination, and the pressure detection means.