An exhaust pipe structure of a motorcycle allowing exhaust air of an exhaust pipe having a branching part to flow into the respective exhaust pipes on the downstream side of the branching part uniformly and smoothly. In an exhaust pipe structure of a motorcycle having an engine attached to a vehicle body frame, an exhaust pipe is connected to an exhaust port of the engine and is provided with a branching pipe that branches into a left-rear-portion exhaust pipe and a right-rear-portion exhaust pipe. A muffler is connected to the left-rear-portion exhaust pipe. A muffler is connected to the right-rear-portion exhaust pipe. The branching pipe is located on a lateral side of a cylinder unit of the engine and above a crankcase cover.