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.