An energy conversion device includes a first acoustic wave generator, a second acoustic wave generator, and an output unit which are provided in a pipe member. The first acoustic wave generator has a thermal energy generator configured to generate thermal energy from electric energy, and converts the thermal energy generated by the thermal energy generator into acoustic energy to generate acoustic wave in working gas by a self-excited thermo acoustic vibration. The second acoustic wave generator converts thermal energy supplied from a heat supply source into acoustic energy and generates acoustic wave in working gas by a self-excited thermo acoustic vibration. The output unit converts the acoustic energy of the acoustic waves from the first acoustic wave generator and the second acoustic wave generator into cold energy to output.