A hydraulic motor equipped with a motor mechanism that is configured to rotate by hydraulic liquid pressure led from a hydraulic liquid pressure source, comprising: a casing that defines a casing chamber which accommodates the motor mechanism, a brake mechanism that is configured to brake the rotation of the motor mechanism, a brake release actuator that is configured to release the braking of the brake mechanism by a brake release pressure led from the hydraulic liquid pressure source, and a throttle passage that is in communication with the casing chamber and extracts a portion of hydraulic liquid that is led into the brake release actuator and leads it to the casing chamber, the motor mechanism includes: a swash plate provided in the casing chamber, a plurality of pistons that are configured to move back and forth following the swash plate by hydraulic liquid pressure, a cylinder block that is configured to rotate relative to the swash plate by the back-and-forth motion of the pistons, and an output shaft that is configured to output the rotation of the cylinder block, the brake mechanism includes: a brake disc that is configured to rotate together with the cylinder block, a friction plate that is attached to the casing, and a brake spring that is configured to compress the brake disc to the friction plate, the brake release actuator includes: an annular brake piston that is movably supported on the casing in a rotation axis direction of the cylinder block, and a brake release pressure chamber into which a brake release pressure that is configured to drive the brake piston to counter the brake spring is led, characterized in that the throttle passage connects the brake release pressure chamber and the casing chamber, the casing chamber is partitioned by the brake disc into an actuator housing chamber which houses the brake release actuator and a swash plate housing chamber which houses the swash plate, an outlet of the throttle passage opens into the actuator housing chamber, and an inlet of a drain passage that is configured to discharge hydraulic liquid of the casing chamber opens into the swash plate housing chamber. a casing that defines a casing chamber which accommodates the motor mechanism, a brake mechanism that is configured to brake the rotation of the motor mechanism, a brake release actuator that is configured to release the braking of the brake mechanism by a brake release pressure led from the hydraulic liquid pressure source, and a throttle passage that is in communication with the casing chamber and extracts a portion of hydraulic liquid that is led into the brake release actuator and leads it to the casing chamber, the motor mechanism includes: a swash plate provided in the casing chamber, a plurality of pistons that are configured to move back and forth following the swash plate by hydraulic liquid pressure, a cylinder block that is configured to rotate relative to the swash plate by the back-and-forth motion of the pistons, and an output shaft that is configured to output the rotation of the cylinder block, a swash plate provided in the casing chamber, a plurality of pistons that are configured to move back and forth following the swash plate by hydraulic liquid pressure, a cylinder block that is configured to rotate relative to the swash plate by the back-and-forth motion of the pistons, and an output shaft that is configured to output the rotation of the cylinder block, the brake mechanism includes: a brake disc that is configured to rotate together with the cylinder block, a friction plate that is attached to the casing, and a brake spring that is configured to compress the brake disc to the friction plate, a brake disc that is configured to rotate together with the cylinder block, a friction plate that is attached to the casing, and a brake spring that is configured to compress the brake disc to the friction plate, the brake release actuator includes: an annular brake piston that is movably supported on the casing in a rotation axis direction of the cylinder block, and a brake release pressure chamber into which a brake release pressure that is configured to drive the brake piston to counter the brake spring is led, an annular brake piston that is movably supported on the casing in a rotation axis direction of the cylinder block, and a brake release pressure chamber into which a brake release pressure that is configured to drive the brake piston to counter the brake spring is led, characterized in that the throttle passage connects the brake release pressure chamber and the casing chamber, the casing chamber is partitioned by the brake disc into an actuator housing chamber which houses the brake release actuator and a swash plate housing chamber which houses the swash plate, an outlet of the throttle passage opens into the actuator housing chamber, and an inlet of a drain passage that is configured to discharge hydraulic liquid of the casing chamber opens into the swash plate housing chamber.