To provide a power generator capable of condensing and reproducing surely evaporated air of a working fluid by using liquid hydrogen as a coolant fluid.

The liquid air injected from a cold insulation storage tank A is made to be sent under pressures to a heat exchanging channel of a metal heat reservoir, and a turbine for power generation and an electric generator thereof are made to be driven in a high speed by the evaporated air where a temperature rise and a dilatation are given, and the evaporated air of the working fluid exhausted in a high speed is made to be condensed and reproduced surely by a cycle where the liquid hydrogen injected from a cold insulation storage tank B is made to be sent under pressure to a heat exchange tube and is made to be returned to the cold insulation storage tank A while the evaporated air exhausted from the turbine for power generation is made to be refrigerated and condensed by heat exchanging, and a cycle where the evaporated hydrogen which has been risen in temperature by heat exchanging with the evaporated air is made to be returned to a liquefied layer by dilatation depressurization and cooling effect of an expansion valve.