Abstract: The invention suggests an unmanned radio-control automotive working machine for safely mowing grass and lawns on dangerous slopes, which includes a carriage on which a power source such as a gasoline engine, a traveling apparatus and a working apparatus of a grass cutter, a lawn mowing blade or the like and, more particularly, the structure of a traveling transmission mechanism of a traveling control apparatus in which a traveling brake functions without fail when a traveling clutch is neutral, and a differential-gear lock and the brake function to effect the braking operation quickly even if the working machine is on a steep slope, and the structure of a brake apparatus installed in a gear case of the traveling transmission. Thus, the invention achieves safety in radio-control operation, and size and weight reduction of the working machine.