PURPOSE: To prevent the generation of an abrupt flow at an excessive flow rate even when an external valve is changed from OFF to ON.

CONSTITUTION: This mass flow controller is provided with a control part 21 for comparing data provided based on measured gas to flow to a sensor pipe in a bridge circuit with set flow rate data inputted from the outside and for controlling the control valve of a main gas duct so as to reduce the difference and a manipulated variable storage part 33 for storing the valve controlled variable of the lower limit flow rate as the lower limit flow rate of the measuring range of measured gas and the valve controlled variable of the upper limit set flow rate as the upper limit flow rate of the measuring range. Further, a standby operation control part 24 is provided to calculate the manipulated variable for controlling the control valve based on the valve controlled variable of the lower limit set flow rate and the valve controlled variable of the upper limit set flow rate inputted from the manipulated variable storage part 23 and the set flow rate while switched from the control part 21 when the external valve is turned off and closed, and the control valve is controlled by the standby operation control part 24 during standby before the external valve is opened again.