An interlock device of a draw-out type circuit breaker, provided with a tripping button that is linked to a tripping mechanism of the draw-out type circuit breaker and an interlock rod that is placed so as to be movable up and down, and constructed so that the tripping button mechanically prevents an operation to raise the interlock rod unless the tripping button is operated to place the draw-out type circuit breaker in the open state, so a power distribution board floor surface or a member fixed on the power distribution board floor surface and the interlock rod interfere with each other, thereby the draw-out type circuit breaker is fixed at a prescribed position in a power distribution board.