Abstract: In a vehicle wherein a rear wheel is supported by a power unit which comprises an integral combination of an engine and a transmission case incorporating a transmission mechanism and which is suspended from a rear part of a vehicle body frame through a damper, a power unit supporting device which supports the power unit for swinging motion at an intermediate portion of the vehicle body frame. The power unit supporting device comprises a front bracket fixed to the vehicle body frame, a rear bracket pivotably connected to the power unit, and leaf spring members having the front and rear ends thereof fixed to the front and rear brackets, respectively, and which cross each other to define substantially an X-shape in side elevation. The power unit supporting device has a relatively high rigidity in the longitudinal direction of the vehicle and in the right and left torsional direction and a relatively low rigidity in the vertical direction.