There is provided an interlock apparatus of a vacuum circuit breaker for adjusting withdrawal of a circuit breaker main body, which is installed in a truck and moves to a connected position in which the circuit breaker main body is connected to a cradle and moves to a disconnected position in which the circuit breaker main body is separated from the cradle within the cradle, to outside of the cradle, includes: a lift including a rotation adjusting plate provided on an upper portion thereof, and moving forwardly and backwardly such that the rotation adjusting plate is inserted into the interior of the cradle or separated from the cradle; and an interlock plate provided within the cradle and rotating according to movement of the rotation adjusting plate so as to be tightly attached to the truck or released from the tightly attached state to thereby adjust withdrawal of the circuit breaker main body to the outside of the cradle.