An external combustion engine comprising a pipe-shaped main container in which a working fluid is sealed flowably in a liquid state, a heated part formed at a location of one end of the main container and heating part of the working fluid in the main container in order to make it evaporate, a cooled part formed at a location next to the heated part toward the other end of the main container and cooling the vapor of the working fluid evaporated at the heated part in order to make it condense, an output unit communicated with the other end of the main container and converting the displacement of the liquid phase part of the working fluid to mechanical energy for output, and a controller alternately performing a heat storage mode making displacement of the liquid phase part of the working fluid stop in order to make the heated part store heat and an output mode allowing displacement of the liquid phase part of the working fluid and taking output from the output unit.