A waterproof box comprising: a box main body having a side wall and accommodating a component in the side wall which offers its dislike of water; a cover having a cover side wall and covering an opening defined by a side wall edge of the box main body; a main body waterproof structure disposed at the side wall edge; a cover waterproof structure disposed at an edge of the cover side wall, the cover waterproof structure securing waterproof by overlaying the main body waterproof structure thereon; pivot points (18,24) for making the cover rotative and detachable relative to the box main body disposed in the main body waterproof structure and the cover waterproof structure, respectively; and a dead end disposed on a wall in which the pivot point of the cover side wall exists, the dead end having an inner face, an outer face parallel to the inner face, and a back face connecting to the inner face and the outer face, the inner face connecting the back face and an opening of the dead end. wherein the dead end is disposed on a main body mating face of the main body waterproof structure and a cover mating face of the cover waterproof structure which both the mating faces oppose to each other by the overlaying, and at an outlet of a small passage induced by a clearance between the main body mating face and the cover mating face, and is formed into a space with a desired size, wherein an outlet reference to the dead end in a position of the outlet of the small passage is set either on the same plane as an outlet reference to the box main body along an extending direction of the side wall or outer than the outlet reference to the box main body, wherein the outlet reference to the dead end is an intersection position of an opening of the dead end and the inner face, and the outlet reference to the box main body is an intersection position of the inner face of the side wall and the upper face of the side wall. a box main body having a side wall and accommodating a component in the side wall which offers its dislike of water; a cover having a cover side wall and covering an opening defined by a side wall edge of the box main body; a main body waterproof structure disposed at the side wall edge; a cover waterproof structure disposed at an edge of the cover side wall, the cover waterproof structure securing waterproof by overlaying the main body waterproof structure thereon; pivot points (18,24) for making the cover rotative and detachable relative to the box main body disposed in the main body waterproof structure and the cover waterproof structure, respectively; and a dead end disposed on a wall in which the pivot point of the cover side wall exists, the dead end having an inner face, an outer face parallel to the inner face, and a back face connecting to the inner face and the outer face, the inner face connecting the back face and an opening of the dead end. wherein the dead end is disposed on a main body mating face of the main body waterproof structure and a cover mating face of the cover waterproof structure which both the mating faces oppose to each other by the overlaying, and at an outlet of a small passage induced by a clearance between the main body mating face and the cover mating face, and is formed into a space with a desired size, wherein an outlet reference to the dead end in a position of the outlet of the small passage is set either on the same plane as an outlet reference to the box main body along an extending direction of the side wall or outer than the outlet reference to the box main body, wherein the outlet reference to the dead end is an intersection position of an opening of the dead end and the inner face, and the outlet reference to the box main body is an intersection position of the inner face of the side wall and the upper face of the side wall.