A present invention provides a device capable of properly measuring the capacitance of a dielectric elastomer by variably manipulating the voltage applied to the dielectric elastomer. A capacitance estimating unit 22 acquires current detection values at a plurality of sampling times in a current reduction period in which, when an output voltage of a power source 10 changes, an energizing current of a dielectric elastomer 1 increases and then gradually decreases according to the change in the output voltage, and estimates the capacitance of the dielectric elastomer 1 on the basis of a model representing a correlation between the time-dependent change of the energizing current and the capacitance of the dielectric elastomer 1 in the current reduction period, and the current detection values.
