Transmission mechanism (130 230) accommodated in a transmission case (50 220) includes an input shaft (131 231) extending upward to connect to a vertical engine (60 210) and an output shaft (132 232) extending horizontally to connect to a working unit (70 240). The engine is mounted on an upper surface portion of the transmission case, and the working unit, motors (20L,20R 250L,250R) and driving-wheel axles of left and right traveling sections (30L,30R 270L,270R), such as crawler belts (33L, 33R), are attached to the transmission case between the traveling sections. The working unit (70) is vertically pivotable about the central axis (DL) of axles of the traveling sections (30L, 30R). The driving wheels (31L, 31R) and motors are positioned adjacent to front end portions of an engine crankshaft (61) positioned near and rearward of the central axis (DL).
