To increase gas sealability between a piston head and a piston skirt.

This heat insulation piston having a heat insulation air layer 5 formed between the piston head 1 and the piston skirt 2 comprises heat insulation rings 17 and 20 disposed on the inner and outer peripheries of the heat insulation layer 5 and a coned disc spring 21 disposed between the heat insulation ring 20 on the outer peripheral side and the heat insulation air layer 5.