There is provided a hydraulic circuit which can further improve a responsive characteristic in a pressure reducing operation and a reliability in the pressure reducing operation of a relief valve device, when a main circuit pressure exceeds a predetermined pressure. A relief valve device for reducing the main circuit pressure in the hydraulic circuit including a hydraulic pump includes a first valve unit having a pilot spool and a pilot spring, a position of the pilot spool being determined by a balance between a throttle pressure supplied from the main circuit via a throttle oil passage and the control pressure and a biasing force of the pilot spring, and releasing the main circuit pressure outward via the throttle oil passage, and includes a second valve unit having a valve piston and a valve spring, a position of the valve piston being determined by a balance between the main circuit pressure and the throttle pressure and the biasing force of the valve spring, and releasing the main circuit pressure outward.