It is possible to apply a correct power to a load even when the output impedance and a load impedance of a signal source are different from a characteristic impedance of a transmission line. The power applied to the load can be expressed by a measurement system error factor, a load coefficient X of the load, and an S parameter of the input signal R. Accordingly, a target input signal decision can decide a target value of the S parameter of the input signal R according to the power desired to be applied to the load, the measurement system error factor, and the load coefficient X of the load. Furthermore, an input signal level control section controls the input signal level so that the S parameter of the input signal R has this target value. This is performed by changing the amplification ratio of an amplification ratio variable amplifier. Thus, it is possible to apply a desired power to the load not depending on whether the impedance is matched or not.