A control center with a functional unit being housed on a partition plate of a functional unit housing space in the control center, the functional unit comprising an interlock mechanism which comprises: an insertion and removal handle's insertion opening which is provided in a functional unit and into which an insertion and removal handle that inserts and removes the functional unit is for being inserted, the functional unit being equipped with a wiring circuit breaker; and an insertion and removal prevention body which prevents the insertion and removal handle from being inserted into the insertion and removal handle's insertion opening when an operation handle mechanism that turns ON and OFF the wiring circuit breaker is in ON state, wherein the interlock mechanism of the functional unit includes a passing-block body (19, 20) which is movably provided with respect to the insertion and removal prevention body in conjunction with the operation handle mechanism coupled to an operation handle that switches ON and OFF states of the wiring circuit breaker; and the passing-block body is prevented from being moved according to the position of the insertion and removal prevention body characterized in that the interlock mechanism is configured such that when the wiring circuit breaker is in ON state and the functional unit is inserted from the outside of the control center, the passing-block body (19, 20) comes in contact with a side portion of the partition plate of the housing space to stop the insertion operation of the functional unit at a position where the distance between a circuit connection section on the control center main body side and a circuit connection on the functional unit side is equal or larger than a necessary electrical insulation distance, wherein the interlock mechanism is further configured such that when the wiring circuit breaker is in OFF state, the functional unit can be further inserted in the control center main body panel from the position where the insertion operation is stopped, the passing-block body (19, 20) being released from movement preventing by the side portion of the partition plate and being located on the upper side of the partition plate of the housing space and the operating handle is prevented from being moved to ON position until the circuit connection section on the control center body side and the circuit connection section on the functional unit side are connected, the interlock mechanism further comprising a pad which is provided on the upper surface of the partition plate and is arranged between the partition plate and the passing-block body (19, 20). an insertion and removal handle's insertion opening which is provided in a functional unit and into which an insertion and removal handle that inserts and removes the functional unit is for being inserted, the functional unit being equipped with a wiring circuit breaker; and an insertion and removal prevention body which prevents the insertion and removal handle from being inserted into the insertion and removal handle's insertion opening when an operation handle mechanism that turns ON and OFF the wiring circuit breaker is in ON state, wherein the interlock mechanism of the functional unit includes a passing-block body (19, 20) which is movably provided with respect to the insertion and removal prevention body in conjunction with the operation handle mechanism coupled to an operation handle that switches ON and OFF states of the wiring circuit breaker; and the passing-block body is prevented from being moved according to the position of the insertion and removal prevention body characterized in that the interlock mechanism is configured such that when the wiring circuit breaker is in ON state and the functional unit is inserted from the outside of the control center, the passing-block body (19, 20) comes in contact with a side portion of the partition plate of the housing space to stop the insertion operation of the functional unit at a position where the distance between a circuit connection section on the control center main body side and a circuit connection on the functional unit side is equal or larger than a necessary electrical insulation distance, wherein the interlock mechanism is further configured such that when the wiring circuit breaker is in OFF state, the functional unit can be further inserted in the control center main body panel from the position where the insertion operation is stopped, the passing-block body (19, 20) being released from movement preventing by the side portion of the partition plate and being located on the upper side of the partition plate of the housing space and the operating handle is prevented from being moved to ON position until the circuit connection section on the control center body side and the circuit connection section on the functional unit side are connected, the interlock mechanism further comprising a pad which is provided on the upper surface of the partition plate and is arranged between the partition plate and the passing-block body (19, 20).