A brake system used in a fluid pressure motor including a cylinder block configured to be rotated by fluid pressure, an output shaft configured to be rotated integrally with the cylinder block, and a case configured to rotatably support the output shaft, the brake system comprising: a brake device configured to cancel brake force by supply of a pressurized working fluid and generate the brake force by discharge of the working fluid; a supply passage through which the working fluid pressurized in a working fluid pressurizing source is supplied to the brake device; a valve device configured to open and close the supply passage; a discharge passage through which the working fluid discharged from the brake device flows; and a restrictor configured to apply resistance to the working fluid flowing through the discharge passage, wherein the valve device has a first connection port connected to the upstream side of the supply passage, the first connection port to which the working fluid is led from the working fluid pressurizing source, a second connection port connected to the downstream side of the supply passage, the second connection port from which the working fluid is led to the brake device, and a valve element (41, 141, 241) provided with a pressure receiving surface facing the first connection port, and the valve element (41, 141, 241) permits communication between the first connection port and the second connection port when pressure of the working fluid led to the first connection port reaches predetermined pressure, and shuts off the communication between the first connection port and the second connection port when the pressure of the working fluid led to the first connection port becomes less than the predetermined pressure. a brake device configured to cancel brake force by supply of a pressurized working fluid and generate the brake force by discharge of the working fluid; a supply passage through which the working fluid pressurized in a working fluid pressurizing source is supplied to the brake device; a valve device configured to open and close the supply passage; a discharge passage through which the working fluid discharged from the brake device flows; and a restrictor configured to apply resistance to the working fluid flowing through the discharge passage, wherein the valve device has a first connection port connected to the upstream side of the supply passage, the first connection port to which the working fluid is led from the working fluid pressurizing source, a second connection port connected to the downstream side of the supply passage, the second connection port from which the working fluid is led to the brake device, and a valve element (41, 141, 241) provided with a pressure receiving surface facing the first connection port, and the valve element (41, 141, 241) permits communication between the first connection port and the second connection port when pressure of the working fluid led to the first connection port reaches predetermined pressure, and shuts off the communication between the first connection port and the second connection port when the pressure of the working fluid led to the first connection port becomes less than the predetermined pressure.