Provided is a hole plug (1) which is provided with a head section (2), a leg section (3) and a flange section (6), and which blocks a hole (9a) in a state wherein the leg section (3) is inserted and locked into a hole (9a) in a plate (9) until the flange section (6) makes contact with the plate (9) and is restricted. The leg section (3) has a substantially cylindrical inner wall (4) which is connected to the head section, and an outer wall (5), in part of which a bendable thin wall section (5a) is formed, and which extends along the inner wall (4) whilst leaving a gap in the space from the inner wall (4), from a turned edge section provided at the tip of the inner wall (4). The hole plug (1) can transition from a first use aspect wherein the plug is locked in the hole (9a) with the thin wall section in a non-bent state, to a second use aspect wherein the plug is pressure welded to the hole (9a) with greater force than in the first use aspect, due to the thin wall section (5a) elastically bending due to external force.