There is provided a waterproof structure for the electrical junction box includes a stepwise portion in which a punched hole has to be provided for molding a locking projection on a peripheral wall of a main-body case. The waterproof structure prevents intrusion of a droplet from an outside into the main-body case via the punched hole and thereby improves waterproof performance. An extended portion 37d is provided on a left wall portion 22 of the main-body case 2 for moving the position of the punched hole which should be provided in the stepwise portion 35 toward the side of the locking projection 33. A hole-sealing portion 47a is provided at a edge portion 42a of the left wall portion 42 of the cover 4, the hole-sealing portion 47a is configured to cover the entire opening of the punched hole 37 moved toward the side of the locking projection 33 in a state where the cover is attached to the main-body case 2.