A pump device, comprising: a rotating body that is rotationally driven about a rotation axis; a pump housing including a suction port and a discharge port that are open to an accommodating chamber accommodating the rotating body, the suction port and the discharge port extending in a shape of an arc-shaped groove, the pump housing includes a first housing member in which the accommodating chamber is provided, and a second housing member in which the suction port and the discharge port are provided; and a relief valve that opens when a hydraulic pressure in the discharge port becomes equal to or higher than a predetermined value, wherein: in the pump device, a fluid is sucked from the suction port and discharged from the discharge port by rotation of the rotating body; the relief valve includes a valve body and a biasing member that biases the valve body in a valve closing direction; the pump device being characterised in that the discharge port includesarr one end in a direction in which the discharge port extends, the one end being shallower than a middle portion of the discharge port; the second housing member includes a relief flow path through which the fluid flows when the relief valve opens, the relief flow path being provided so as to be open to a groove bottom surface of the one end of the discharge port; and the valve body and the biasing member of the relief valve and an opening of the relief flow path are arranged in a direction parallel to the rotation axis, the opening being provided in the groove bottom surface, the valve body and the biasing member of the relief valve are accommodated in the relief flow path. a rotating body that is rotationally driven about a rotation axis; a pump housing including a suction port and a discharge port that are open to an accommodating chamber accommodating the rotating body, the suction port and the discharge port extending in a shape of an arc-shaped groove, the pump housing includes a first housing member in which the accommodating chamber is provided, and a second housing member in which the suction port and the discharge port are provided; and a relief valve that opens when a hydraulic pressure in the discharge port becomes equal to or higher than a predetermined value, wherein: in the pump device, a fluid is sucked from the suction port and discharged from the discharge port by rotation of the rotating body; the relief valve includes a valve body and a biasing member that biases the valve body in a valve closing direction; the pump device being characterised in that the discharge port includesarr one end in a direction in which the discharge port extends, the one end being shallower than a middle portion of the discharge port; the second housing member includes a relief flow path through which the fluid flows when the relief valve opens, the relief flow path being provided so as to be open to a groove bottom surface of the one end of the discharge port; and the valve body and the biasing member of the relief valve and an opening of the relief flow path are arranged in a direction parallel to the rotation axis, the opening being provided in the groove bottom surface, the valve body and the biasing member of the relief valve are accommodated in the relief flow path. in the pump device, a fluid is sucked from the suction port and discharged from the discharge port by rotation of the rotating body; the relief valve includes a valve body and a biasing member that biases the valve body in a valve closing direction; the pump device being characterised in that the discharge port includesarr one end in a direction in which the discharge port extends, the one end being shallower than a middle portion of the discharge port; the second housing member includes a relief flow path through which the fluid flows when the relief valve opens, the relief flow path being provided so as to be open to a groove bottom surface of the one end of the discharge port; and the valve body and the biasing member of the relief valve and an opening of the relief flow path are arranged in a direction parallel to the rotation axis, the opening being provided in the groove bottom surface, the valve body and the biasing member of the relief valve are accommodated in the relief flow path.