An electric inertia control device 5A simulates the behavior of an inertial body having a predetermined set moment of inertia Jset by means of a dynamometer, and is provided with: an inertia compensator 51A which generates a torque signal by multiplying a signal obtained by subtracting a shaft torque detection signal T12 from a higher-level command torque signal T* by the ratio of a moment of inertia J1 of the dynamometer to the set moment of inertia Jset, and generates an inertia compensation torque signal Tref by summing the torque signal and the shaft torque detection signal J1; and a resonance suppression control circuit 53A which uses the inertia compensation torque signal Tref and the shaft torque detection signal T12 to generate a torque current command signal T1 in such a way as to suppress resonance in a mechanical system including a test piece and the dynamometer.