To effectively prevent an erroneous connection from occurring between pilot control valves and pilot operation valves in a production line even if a hydraulic device comprises a large number of pilot control valves and pilot operation valves.

This hydraulic device of a work machine comprises the plurality of pilot control valves controlled by a pilot pressure from pilot operation valves to control a hydraulic actuator. The hydraulic device further comprises a first hydraulic block to which the plurality of pilot operation valves are connected and a second hydraulic block to which the plurality of pilot control valves are connected. The first hydraulic block and the second hydraulic block are fixedly tightened to each other. Oil paths corresponding to the first hydraulic block and the second hydraulic block are formed so that, when the first hydraulic block and the second hydraulic block are fixedly tightened with each other, the corresponding pilot operation valves and the pilot control valves can be connected to each other.