A lock structure comprising: an engaged body; an engaging body that allows the engaged body to be inserted thereinto and removed therefrom along inserting and removing directions opposite to each other, the engaging body being capable of locking the inserted engaged body in the inserting direction and the removing direction, wherein the engaged body includes: an engaged main body that is insertable into and removable from the engaging body; and an engaged protrusion that protrudes from an outer wall surface of the engaged main body, and the engaging body includes: first and second engaging walls (23, 24) arranged so as to be opposed to each other with a gap therebetween in a direction orthogonal to the inserting and removing directions; third and fourth engaging walls (25, 26) arranged so as to be opposed to each other with a gap therebetween in a direction orthogonal to the inserting and removing directions and to the direction in which the first and second engaging walls (23, 24) are arranged so as to be opposed to each other; a housing space that is an internal space surrounded by inner wall surfaces of the first to fourth engaging walls (23 to 26) and in which the engaged main body is housed; an insertion port through which the engaged main body is inserted into the housing space from a distal end (11a1) of an end portion thereof on the inserting direction side; a locking hole that is a through hole provided in the second engaging wall and through which the engaged protrusion is inserted when the engaged main body is housed in the housing space; a communicating port that communicates the housing space to outside on the inserting direction side of the locking hole; and a covering portion that covers an end portion of the housed engaged main body on the inserting direction side, characterized in that the covering portion has an end portion of the first engaging wall on the inserting direction side, a first covering wall portion disposed so as to be opposed to the end portion with a gap therebetween and such that the end portion of the housed engaged main body is interposed between the first covering wall portion and the end portion. an engaged body; an engaging body that allows the engaged body to be inserted thereinto and removed therefrom along inserting and removing directions opposite to each other, the engaging body being capable of locking the inserted engaged body in the inserting direction and the removing direction, wherein the engaged body includes: an engaged main body that is insertable into and removable from the engaging body; and an engaged protrusion that protrudes from an outer wall surface of the engaged main body, and the engaging body includes: first and second engaging walls (23, 24) arranged so as to be opposed to each other with a gap therebetween in a direction orthogonal to the inserting and removing directions; third and fourth engaging walls (25, 26) arranged so as to be opposed to each other with a gap therebetween in a direction orthogonal to the inserting and removing directions and to the direction in which the first and second engaging walls (23, 24) are arranged so as to be opposed to each other; a housing space that is an internal space surrounded by inner wall surfaces of the first to fourth engaging walls (23 to 26) and in which the engaged main body is housed; an insertion port through which the engaged main body is inserted into the housing space from a distal end (11a1) of an end portion thereof on the inserting direction side; a locking hole that is a through hole provided in the second engaging wall and through which the engaged protrusion is inserted when the engaged main body is housed in the housing space; a communicating port that communicates the housing space to outside on the inserting direction side of the locking hole; and a covering portion that covers an end portion of the housed engaged main body on the inserting direction side, characterized in that the covering portion has an end portion of the first engaging wall on the inserting direction side, a first covering wall portion disposed so as to be opposed to the end portion with a gap therebetween and such that the end portion of the housed engaged main body is interposed between the first covering wall portion and the end portion.