A saddle ride type all-terrain vehicle includes an engine, a front wheel and rear wheels, a saddle type rider's seat, and a rear fender provided so as to cover the surroundings of the saddle type rider's seat and the rear wheels. The vehicle further includes an exhaust pipe led out to the vehicle body rear side from the engine, a muffler connected to the exhaust pipe, and an oxygen concentration sensor provided in the vicinity of a connection portion between the exhaust pipe and the muffler, wherein the oxygen concentration sensor is located inside the rear fender.