Masking member, and method for coating hollow member

A masking member comprising:

• a masking main body that is formed of an elastic material and that closes an opening portion of a hollow member by being inserted into the opening portion;
• and
• a passage portion that is formed at the masking main body, that opens on an outer peripheral surface of the masking main body, and that connects an outside and an inside of the hollow member by at least a part of an opening at the outer peripheral surface being exposed to the outside of the hollow member in a case in which the masking main body, in a state of closing the opening portion, moves in a direction opposite from an insertion direction, wherein:
• an annular recess extending along a circumferential direction is formed at an inner peripheral surface of the opening portion in the hollow member, and
• the masking main body includes a restriction portion that overhangs radially outward from a distal end surface side in the insertion direction and is fitted into the recess to restrict movement of the masking main body in the direction opposite from the insertion direction.