A power unit supporting structure for minimizing rotational vibration about the center of gravity of a power unit, and secondary vibration in the direction of a cylinder axis line of the power unit. The structure includes a link mechanism having a first frame side link swingably connected to a first pivot on the side of a rear frame, and first power unit side links swingably connected to a third pivot on a side of the power unit. The first frame side link and the first power unit side links are swingably connected by a second pivot. A first line segment connecting the first pivot and the second pivot is disposed approximately perpendicular to a cylinder axis line. A second line segment connecting the second pivot and the third pivot is approximately parallel to a third line segment connecting the third pivot and the center of gravity of the power unit.