Piston of internal combustion engine and manufacturing method of piston

The present invention relates to a piston of an internal combustion engine, including a piston body (11), a pair of skirt sections (12A, 12B), a pair of side wall sections (13A, 13B), and pin hole sections (14A, 14B), and a cavity is formed by the bottom wall surface of the piston body, inner peripheral wall surfaces of the skirt sections, and inner wall surfaces of the side wall sections. In the present invention, a bulge section (20) that extends in a direction form a region of an outer wall surface of a side wall section adjacent to the piston body and a skirt section (AR1) toward a region of the outer wall surface of the side wall section adjacent to a lateral part of a pin hole section (AR3) is provided in the outer wall surface of the side wall section.