To provide a separate type underwater lighting system which has a light section and a battery container separated, having a battery and its safety is enhanced by preventing secondary damages or the like, while monitoring a connecting condition of a connector and cutting off power supply of a battery container to the connector, when the connector comes off or has practically or comes off.

This underwater lighting system is provided with a battery container having a waterproof battery and a waterproof connector 15, and a lighting section 11 having a waterproof ramp 12 and the waterproof connector 15 provided removably with the connector of the battery container, wherein when the connector of the lighting section 11 connected to the connector of the battery container is disconnected or has become virtually the same condition as the disconnected condition, a safety circuit 21 is provided so as to shield the electricity supplied to the connector of the battery container and a pressure releasing valve is also provided in the battery container.