PURPOSE: To reduce the generation of engine slap noise and a useless volume through reduction of a thermal expansion amount of the top land of a piston skirt and to improve startability through suppression of reduction of a compression ratio.

CONSTITUTION: A heat insulating piston comprises a piston skirt 2 formed of a metallic material; and a piston head 1 formed of a ceramic material. An annular groove 4 is formed in the top land part 9 of the piston skirt 2 and a stress exerting ring member 3 formed of a material having a thermal expansion factor lower than that of a metallic material of which the piston skirt 2 is formed is fitted in the inner peripheral surface 18 on the piston ring groove 15 side of the annular groove 4. A tensile stress is exerted on the outer peripheral part 19 of the piston skirt 2 by the stress exerting ring member 3 at an ordinary temperature period.