The utility model provides a split-type rotary motor casing of an excavating machine. The rotary motor casing comprises a casing, wherein an inner chamber is formed inside the casing; a swash plate platform is arranged inside the inner chamber; a swash plate platform through hole is formed on the swash plate platform, a swash plate is mounted on the swash plate platform and adopts a truncated cylindrical body, the lower end surface of the swash plate is a circular plane, the upper end of the swash plate is an elliptic inclined plane, and a swash plate through hole is formed on the swash plate. The rotary motor casing can be manufactured by conventional common processing equipment due to the fact that the inner part of the casing dispenses with an inclined plane, thereby reducing the processing difficulty and cost; the previously needed inclined plane is arranged on the swash plate, and the swash plate can be mounted inside the casing during assembly; the swash plate can be independently manufactured, thereby effectively reducing the processing difficulty and cost; and as an independent component, the swash plate can be directly replaced without scrapping the whole motor casing once the inclined plane of the swash plate is abraded, thereby effectively prolonging the service life of the motor casing and saving resources.