A lock structure comprising: an engaged body; and an engaging body capable of inserting and removing the engaged body along insertion and removal directions opposite to each other, and capable of locking the inserted engaged body in the insertion direction and the removal direction, respectively, wherein the engaged body has first and second engaged walls (13, 14) disposed opposite to each other at an interval in an orthogonal direction to the insertion and removal directions, a connection wall that connects end portions on the insertion direction side of the first and second engaged walls (13, 14), and an engaged protrusion protruding from an outer wall surface of the second engaged wall, the engaging body has first and second engaging walls (23, 24) that are disposed opposite to each other at an interval in an opposite arrangement direction of the first and second engaged walls (13, 14) and in which a space between respective inner wall surfaces (23a, 24a) is defined as an accommodation space of the engaged body, an engaging protrusion protruding from the inner wall surface of the second engaging wall and capable of locking the engaged protrusion on the removal direction side when the engaged body inserted into the accommodation space from the connection wall side is in an accommodated state, and a third engaging wall disposed opposite to the respective inner wall surfaces (23a, 24a) at an interval between the first and second engaging walls (23, 24), a space is formed between the first engaging wall and the third engaging wall, a space is formed between the second engaging wall and the third engaging wall, the third engaging wall has a locker capable of locking the connection wall on the insertion direction side when in the accommodated state, and the second engaging wall has a shape and arrangement capable of blocking liquid going straight from the outside toward a part between the connection wall and the locker disposed opposite to each other in the insertion and removal directions when in the accommodated state. an engaged body; and an engaging body capable of inserting and removing the engaged body along insertion and removal directions opposite to each other, and capable of locking the inserted engaged body in the insertion direction and the removal direction, respectively, wherein the engaged body has first and second engaged walls (13, 14) disposed opposite to each other at an interval in an orthogonal direction to the insertion and removal directions, a connection wall that connects end portions on the insertion direction side of the first and second engaged walls (13, 14), and an engaged protrusion protruding from an outer wall surface of the second engaged wall, the engaging body has first and second engaging walls (23, 24) that are disposed opposite to each other at an interval in an opposite arrangement direction of the first and second engaged walls (13, 14) and in which a space between respective inner wall surfaces (23a, 24a) is defined as an accommodation space of the engaged body, an engaging protrusion protruding from the inner wall surface of the second engaging wall and capable of locking the engaged protrusion on the removal direction side when the engaged body inserted into the accommodation space from the connection wall side is in an accommodated state, and a third engaging wall disposed opposite to the respective inner wall surfaces (23a, 24a) at an interval between the first and second engaging walls (23, 24), a space is formed between the first engaging wall and the third engaging wall, a space is formed between the second engaging wall and the third engaging wall, the third engaging wall has a locker capable of locking the connection wall on the insertion direction side when in the accommodated state, and the second engaging wall has a shape and arrangement capable of blocking liquid going straight from the outside toward a part between the connection wall and the locker disposed opposite to each other in the insertion and removal directions when in the accommodated state.