The waterproof box includes a body case and a cover mounted to the body case by making a hook portion at one end of the cover engaged with a projection at one end of the body case and rotatably moving the cover around the hook portion. The one end of the respective body case and the cover has a double-walled structure having an outer wall and an inner wall. With the cover mounted to the body case, the outer wall of the body case is located inside the outer wall of the cover, the inner wall of the cover is located inside the outer wall of the body case, the inner wall of the body case is located inside the inner wall of the cover, and the outer wall of the body case and the inner wall of the cover are arranged with a space between each other.