A motortricycle with oscillation mechanism including left and right suspension arms respectively swingably mounted onto a vehicle body frame, rear wheels mounted respectively onto the outer portions of the left and right suspension arms. An oscillation mechanism permitting leftward and rightward oscillation of the vehicle body frame relative to the side of the suspension arms is provided between the suspension arms and the vehicle body frame, and an engine for driving the left and right rear wheels is mounted onto the vehicle body frame. Since the engine of the motortricycle is mounted on the vehicle body frame rather than on the suspension arms, weight on the suspension arms can be largely reduced, and the riding comfort can be further enhanced.