A steam engine has a fluid container, a heating device and a cooling device provided at the fluid container for heating and cooling working fluid filled in the fluid container, so that a part of the working fluid is heated and vaporized to move the liquid-phase working fluid in one direction. When the vaporized steam is cooled and liquidized, the pressure of the working fluid in the fluid container is decreased, to thereby move the liquid-phase working fluid in the backward direction. Kinetic energy is thereby generated by using the back and forth movement of the working fluid. The heating device has multiple through-holes, through which the working fluid flows and heated by a heating surface (an inner surface of the through-holes) of the heating device, wherein a diameter “d” of the through-hole is made almost equal to or smaller than a depth of heat penetration “δ”, which is determined by the following formula: δ=√{square root over (2a/ω)} wherein “a” is a heat diffusivity of the working fluid, and “ω” is an angular frequency of the working fluid during the working fluid is periodically moved back and forth.