A frame structure of a vehicle 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 with an inner space for accommodating a running-power transmission path for transmitting power from an engine to drive wheels via a HST unit. The flywheel housing has a first end connected to the engine and a second open end opposite to the first end along the longitudinal axis of the vehicle. 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 has 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 HST unit, and an opening surrounded by the support surface. The opening serves 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 HST unit is accommodated within the flywheel housing.