To inspect a change of discharge resistance of a pump based on a general characteristic value used for operation control of the pump.

A data acquisition section 11 acquires as an input characteristic value for calculation 2A a flow rate at control Q1 and a pump head at control H1 indicating an operation point at control R1 and also acquires a rotational speed ratio at control INV1 as an input characteristic value for comparison 2B. A characteristic value calculation section 17 calculates as a reference characteristic value 4A a characteristic value of the pump specified from a reference operation point R0 in case of operating the pump at a reference rotational speed N0, based on a reference pump head curve A0 of a reference pump head curve function expression 15A of a storage section 15 and the input characteristic value for calculation 2A acquired by the data acquisition section 11. A characteristic value comparison section 18 judges the change of discharge resistance of the pump, by comparing a comparison characteristic value 4B composed of the input characteristic value for comparison 2B acquired by the data acquisition section 11 and the reference characteristic value 4A obtained by the characteristic value calculation section 17.