A hydraulic circuit, comprising: a hydraulic power supplier including a tank configured to store hydraulic oil, and a hydraulic pump coupled to the tank and configured to feed hydraulic pressure oil; a stack valve coupled to the hydraulic power supplier, the stack valve including a direction switching valve configured to control supply/discharge of the hydraulic pressure oil from the hydraulic power supplier to a hydraulic device; a multifunction valve provided in the vicinity of the hydraulic device, the multifunction valve including (i) a first stop valve and a second stop valve which respectively open/close a first supply/discharge circuit and a second supply/discharge circuit for the hydraulic device, and (ii) a bypass circuit positioned closer to the stack valve than the first stop valve and the second stop valve, the bypass circuit including a third stop valve; and a composite valve coupled to the hydraulic power supplier, the stack valve, and the multifunction valve, wherein the composite valve includes: a multifunction valve-side first passage including a multifunction valve-side first stop valve configured to open/close communication between the multifunction valve and the stack valve; a multifunction valve-side second passage including a multifunction valve-side second stop valve configured to open/close communication between the multifunction valve and the stack valve; a pump-side passage including a pump-side stop valve configured to open/close communication between the hydraulic pump and the stack valve; a tank-side passage including a tank-side stop valve configured to open/close communication between the tank and the stack valve; a pump-side bypass circuit branching off from the pump-side passage at a position closer to the hydraulic pump than the pump-side stop valve, the pump-side bypass circuit including a pump-side bypass stop valve configured to open/close communication with the multifunction valve-side first passage; and a tank-side bypass circuit branching off from the tank-side passage at a position closer to the tank than the tank-side stop valve, the tank-side bypass circuit including a tank-side bypass stop valve configured to open/close communication with the multifunction valve-side second passage. a hydraulic power supplier including a tank configured to store hydraulic oil, and a hydraulic pump coupled to the tank and configured to feed hydraulic pressure oil; a stack valve coupled to the hydraulic power supplier, the stack valve including a direction switching valve configured to control supply/discharge of the hydraulic pressure oil from the hydraulic power supplier to a hydraulic device; a multifunction valve provided in the vicinity of the hydraulic device, the multifunction valve including (i) a first stop valve and a second stop valve which respectively open/close a first supply/discharge circuit and a second supply/discharge circuit for the hydraulic device, and (ii) a bypass circuit positioned closer to the stack valve than the first stop valve and the second stop valve, the bypass circuit including a third stop valve; and a composite valve coupled to the hydraulic power supplier, the stack valve, and the multifunction valve, wherein a multifunction valve-side first passage including a multifunction valve-side first stop valve configured to open/close communication between the multifunction valve and the stack valve; a multifunction valve-side second passage including a multifunction valve-side second stop valve configured to open/close communication between the multifunction valve and the stack valve; a pump-side passage including a pump-side stop valve configured to open/close communication between the hydraulic pump and the stack valve; a tank-side passage including a tank-side stop valve configured to open/close communication between the tank and the stack valve; a pump-side bypass circuit branching off from the pump-side passage at a position closer to the hydraulic pump than the pump-side stop valve, the pump-side bypass circuit including a pump-side bypass stop valve configured to open/close communication with the multifunction valve-side first passage; and a tank-side bypass circuit branching off from the tank-side passage at a position closer to the tank than the tank-side stop valve, the tank-side bypass circuit including a tank-side bypass stop valve configured to open/close communication with the multifunction valve-side second passage.