To provide a technology superior in workability, without reducing operability, in a hydraulic interlock system arranged in an explosion-proof area having a plurality of doors.

This hydraulic interlock system is arranged in the explosion-proof area having the plurality of doors; and connects a detecting valve and a controller by a first tube for transmitting fluid pressure to the detecting valve; and connects a lock mechanism part and the controller by a second tube for transmitting the fluid pressure to the lock mechanism part. An individual pipe is arranged in a frame body, and the second tube is stored in this individual pipe, and passes through into the frame body, and is arranged via a pipe feeding metal fitting and the detecting valve periphery. A common pipe reaching the controller periphery is arranged by storing the first tube and the second tube from the detecting valve periphery by an assembly on the detecting valve periphery of the first tube and the second tube. The common pipes in the same number as the number of doors are collected in the controller.