The purpose of the invention is to enable a crawler tractor to brake and stop certainly without applying a load to an engine and a driving mechanism, and without complicated operation. An operation link links a conic linkage (53) which links a steering wheel (7) with a main speed change lever (55) of the crawler tractor, and with an operation mechanism of a brake pedal (54). A neutral return mechanism for the operation link is provided. The operation link neutral return mechanism comprises a hook-like cam lever (61). When the brake pedal is depressed, the main speed change lever is moved to its neutral position before braking force occurs, and then, the brake is actuated. Accordingly, engine brake is used effectively, and the brake can be miniaturized.