A hydraulic motor equipped with a motor mechanism, the motor mechanism being configured to rotate by hydraulic liquid, the hydraulic liquid being supplied from a hydraulic liquid pressure source through one of a first motor passage and a second motor passage, the hydraulic liquid being discharged to the hydraulic pressure source through the other of the first motor passage and the second motor passage, comprising: a casing that defines a casing chamber which accommodates the motor mechanism, and a flushing passage that is in communication with the casing chamber and extracts a portion of the hydraulic liquid from a low pressure side among the first motor passage and the second motor passage and leads it to the casing chamber, wherein 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, wherein the casing includes: a base plate in which the first motor passage and the second motor passage are provided, and a case that supports the output shaft and defines the casing chamber together with the base plate, characterized in that the flushing passage is defined by a base-side flushing through hole that is formed in the base plate and a case-side flushing through hole that is formed in the case and is in communication with the base-side flushing through hole. a casing that defines a casing chamber which accommodates the motor mechanism, and a flushing passage that is in communication with the casing chamber and extracts a portion of the hydraulic liquid from a low pressure side among the first motor passage and the second motor passage and leads it to the casing chamber, wherein 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, wherein the casing includes: a base plate in which the first motor passage and the second motor passage are provided, and a case that supports the output shaft and defines the casing chamber together with the base plate, a base plate in which the first motor passage and the second motor passage are provided, and a case that supports the output shaft and defines the casing chamber together with the base plate, characterized in that the flushing passage is defined by a base-side flushing through hole that is formed in the base plate and a case-side flushing through hole that is formed in the case and is in communication with the base-side flushing through hole.