To provide a flow controller and a test method therefor which enable testing of the flow control of a process gas passing through a fluid path during operation of semiconductor manufacturing apparatuses.

While the flow control is performed to adjust the flow rate through the fluid path 4 to a flow rate set value, a predetermined number of pieces of test sampling information is collected and associated with the flow rate set value for storage. The test sampling information is made up of a detected flow rate value of the process gas, a detected pressure value, and valve drive control information delivered to a flow control valve mechanism 7. Then, coefficients (A) of association are sequentially determined which indicate the associations of the predetermined number of detected flow rate values and pieces of valve drive control information, which are stored as the test sampling information. When the value of a coefficient (A) of association is out of the range of predetermined threshold values, a difference is determined between the valve drive control information made available based on a newly received detected flow rate value and the reference valve drive control information obtained with reference to a valve property information table K1 pre-registered for testing. This difference is employed as test information.