The invention provides a waterproof switch which can electrically open and close an door of a vehicle body by a switch, can achieve a seal between a waterproof switch and a panel and a seal against an inner portion of the waterproof switch by one seal member, and previously make a seal member hold in a side of the waterproof switch at a time of assembling. The waterproof switch comprises: a base (1) having a seal surface (17); a push rod (3) moving against an urging force so as to open or close a contact point; a seal member (5) having a head cover portion (31), a panel seal portion (33) and a base seal portion (35); and a case (7) provided with a mounting and engaging portion (37), and a seal assist portion (39) pressing the base seal portion (35) to the seal surface (17) of the base (1) in a mounting state of the mounting and engaging portion (37) and closely attaching the panel seal portion (33) to a panel (OP) at a time of supporting the panel seal portion (33) so as to mount the base (1) to a side of the panel (OP).