To provide an excellent hook made of synthetic resin, which is equipped with a durable fall-off stopper, is light in weight, and facilitates both locking and disengaging operations for a member to be connected, and in which the member to be connected is prevented from being accidentally disengaged.

The hook made of the synthetic resin is provided with a hook-shaped main body (1) and the fall-off stopper (2) which is attached to the main body in a freely opened/closed manner. The hook is characterized in that it is separately equipped with an opening/closing shaft (22) which opens/closes the main body (1) of the hook at the time of the locking operation and with a turning shaft (33) which becomes a shaft for opening/closing at the time of the disengaging operation.