To provide a projection failure detector of a breaker for a furnace capable of certainly preventing burning of a projection coil for projecting the breaker in the breaker for the furnace.

A projection failure detector includes: a breaker 8 for opening and closing a main circuit of an arc furnace for steelmaking 1; a projection coil 17 for projecting the breaker 8; a current detection circuit 18 which detects current flowing to the projection coil 17; and a determination circuit 13 which detects a projection failure of the breaker 8. The determination circuit 13 detects the projection failure of the breaker 8 when a current detected by the current detection circuit 18 is larger than a predetermined reference value when the breaker 8 at an open state is projected.