A wheel type work machine having improved ease of assembly and a compact-sized traveling system power transmission mechanism. The wheeled work machine comprises a traveling body (2) having an engine (7) mounted at the rear of a machine frame (6) supported by front and rear wheels (4, 5) and the traveling system power transmission mechanism (8) for transmitting power from the engine (7) to the rear wheels (5). The traveling system power transmission mechanism (8) comprises a rear wheel differential device (38) disposed on the front side of the engine (7), a hydrostatic transmission (35) disposed on the front side and the rear wheel differential device and receiving the power from the engine (7), and a mechanical transmission device (37) disposed between the hydrostatic transmission (35) and the rear wheel differential device (38) and transmitting the power from the hydrostatic transmission (35) to the rear wheel differential device (38). The rear wheel differential device (38), the mechanical transmission device (37), and the hydrostatic transmission (35) are formed integrally with the engine (7).