To provide a hole plug having its weight trimmed by decreasing the amount of a thermosoftening member while keeping adhesion to a hole.

In the hole plug 10, a cylindrical outer body 24 is inserted into a hole formed in a fitting object. A flange part 30 extends outward in the radial direction from a first circumferential end 52 which is one of the circumferential ends of the outer body 24, and inclines toward a second circumferential end 54 which is the other circumferential ends of the outer body 24. A protrusion is formed on the circumference of the outer body 24 and protrudes in the radial direction from the other second circumferential end 54. An engagement part engages with an edge of the hole. The first thermosoftening member 60 is attached on the outer peripheral surface of the body between the protrusion and the first circumferential end 52 and set so as to be situated at the inner peripheral side of the hole. The protrusion is situated on upper side of the hole, while the flange part 30 is attached to the fitting object so as to be located at an owner part of the hole.