Disclosed is a plug interlock device for a vacuum circuit breaker. Only after a plug is completely mounted to a connector, an insertion or withdrawal operation by a vacuum circuit breaker is performed. Accordingly, while a breaker body is moved to a ‘RUN’ position from a ‘TEST’ position, or when an operation is performed at a ‘RUN’ position, the plug may be prevented from being separated from the connector. This may prevent an accident.