Provided are: a power generator including a dielectric elastomer element with an elastomer layer and electrodes sandwiching the layer; an intermediate power storage including a specific number of capacitors to receive output power from the power generator; a storage unit to receive output power from the intermediate power storage; and a controller for setting control by switching a mode between an input mode and an output mode. In the input mode, some number of the capacitors of the intermediate power storage are connected to the power generator such that a series number is an input series number of less than or equal to the specific number. In the output mode, some number of the capacitors are connected to the storage unit such that the series number is an output series number which is smaller than the input series number.