To provide a unit by calculating, the phase and amplitude of a response wave, when inputting sweep waves.

A sweep wave generator 1 produces sample data fsin on the sweep wave, sample data fcos of a waveform different from the sweep wave in phase by 90°, and data Δθ on an amount of change in phase at respective sampling times. The sweep wave fsin is impressed on a physical object 2, such as a specimen. Sample data fo on response waves, outputted from the physical object 2 and respective data outputted from the wave generator 1, are inputted into an arithmetic unit 3 to calculate the amplitude A and phase difference δ of the response wave fo, based on values Fs and Fc found, by integrating fo×fsin×Δθ and fo×fcos×Δθ by a period of a positive integral multiple of half a cycle. The use of this arithmetic circuit makes it possible to form a multishaft testing machine for driving a plurality of shafts, by the same sweep waves with its phase shifted without requiring special hardware.