The present invention relates to a scooter-type vehicle comprising a rear body (7) a housing box (8) disposed in the rear body (7), and a unit swing type engine (4) provided under the rear body (7), wherein a reference line (X₁-X₁) is established on the upper side profile of the unit swing type engine (4) so that the upper end of the upper side of the unit swing type engine (4) is placed under the reference line (X₁-X₁). It is therefore sufficient to consider the relation between the reference line and the bottom of the housing box (8) during oscillation of the unit swing type engine (4). It is thus possible to simplify the locus and range of the oscillation and make attempts to increase the stroke amount of a rear cushion unit (18), decrease the height of a seat (5) and increase the volume of the housing box (8). In addition, since the upper end of the upper side of the unit swing type engine (4) is placed under the reference line (X₁-X₁), it is possible to avoid the interference with the vehicle body (7) and improve the workability when the unit swing type engine (4) is attached to and detached from the vehicle body (7).