At the time of casting a structural material for a casing, metal pipes to be used as passages to and from a tilt actuator of a swash plate are integrally embedded in a cast body of the structural material. In a casting stage of the structural material for the casing, metal pipes are set in position within a casting mold, and then molten metallic material is introduced into the mold. A main casing for a hydraulic motor is formed out of the cast structural material by finishing its inner and outer peripheral surfaces and outer ends of embedded metal pipes. The resulting casing has the metal pipe conduits embedded in its cylindrical body portion from its open end toward its bottom portion with cylinders for a tilt actuator, the embedded metal pipe conduits providing passages on the inner peripheral side for supplying and discharging tilt control hydraulic fluid to and from the tilt actuator.