To easily stop a machine body in emergency by disengaging a main clutch at least via an operation in one of two directions of an auxiliary clutch lever.

When a control handle 5 is unexpectedly lifted by the torque reaction of drive wheels at the time of a reverse travel, an auxiliary clutch lever 17 is pulled from below. The auxiliary clutch lever 17 is oscillated downward around a second horizontal axis Pc, a second operation section 17a presses an operated arm 10c of a main clutch lever 10, the main clutch lever 10 is switched form the on-position to the off-position, and the off-state of a main clutch 3 can be easily attained. When the auxiliary clutch lever 17 is operated downward, a machine body can be easily stopped in emergency. The main clutch lever 10 can be switches in the similar movement via the forward action of the auxiliary clutch lever 17.