Provided is a safety device configured to freely disassemble a safety device unit. The safety device unit has: an actuator that is pre-tensioned by an elastic member to a direction in which a trip device of the circuit breaker operates; and a lever which is configured to protrude from the bottom surface of a base by preload force from the actuator, and to lock the actuator in a position where thetrip device is not operated in a state where the projection is pushed back.