In a frame structure of a vehicle that includes a flywheel housing, an intermediate housing and a transmission case that are connected to each other along a longitudinal axis of the vehicle to constitute a vehicle frame, the intermediate housing has a hollow shape with a first end and a second end located along the longitudinal axis of the vehicle, the first end having an abutting surface against which the second end of the flywheel housing abuts, a support surface located radially inwardly of the abutting surface so as to support the forward/rearward movement switching unit, and an opening surrounded by the support surface, the opening serving as a first-end opening of the intermediate housing along the longitudinal axis of the vehicle. The abutting surface and the support surface along the longitudinal axis of the vehicle are located so that at least a portion of the forward/rearward movement switching unit is accommodated within the flywheel housing.