A pressure-type flow rate control device includes a restriction part, a control valve disposed upstream of the restriction part, an upstream pressure sensor, a downstream pressure sensor, and a controller that diagnoses flow rate control by using pressure drop data on a flow passage between the control valve and the restriction part and reference pressure drop data, wherein a close command is issued to the control valve and a shutoff valve provided downstream of the downstream pressure sensor, and the controller determines whether a predetermined critical expansion condition is satisfied by using outputs of the upstream pressure sensor and the downstream pressure sensor after the control valve is closed, and diagnoses flow rate control by using the pressure drop data acquired during a period in which the predetermined critical expansion condition is satisfied.