The invention provides a switch cabinet and an interlocking device of a switch cabinet door and a circuit breaker handcart. The interlocking device comprises a fixing frame and a sliding block installed on the fixing frame in a guided moving mode. The sliding block has a stopping position and an unlocking position in the moving stroke. A cabinet door can be prevented from being opened when the sliding block is located at the stopping position, and the cabinet door can be opened only when the sliding block is located at the unlocking position. The beneficial effects are as follows: the interlocking device can achieve interlocking between a switch cabinet door and a circuit breaker handcart; after the cabinet door is closed, the sliding block is located at the stopping position, the stoppingface of the sliding block is in stopping fit with the matching face of a baffle, and the cabinet door cannot be opened, so that safety hazards caused by the fact that a maintainer opens the cabinet door carelessly when the circuit breaker handcart is located at a working position are prevented; and when the circuit breaker handcart returns to a testing position from the working position, the sliding block can move to the unlocking position from the stopping position under the pushing action force of a pushing structure on the circuit breaker handcart, and the cabinet door can be opened, so that the safety of maintenance personnel is ensured.