The present invention provides a surfing board leash tangle prevention instrument which prevents a leash on a surfing board from being stepped on, without being a hindrance or large resistance when on the move in the water. The leash for linking the surfing board to a user is attached with a weight member for sinking the leash into the sea or water. In order to make the weight member movable in the longitudinal direction of the leash, the weight member comprises a ring member having a through-hole which is larger than the external diameter of the leash.