NOVELTY - The apparatus has a support plate (11) supporting a battery module (12), where a lower plate (14) is thermally contacting bottom surfaces of the battery module, and an upper plate (15) is placed on a bottom surface of the lower plate to define cooling spaces between the plates. A set of reinforcing projections is provided on the plates and projected into the cooling spaces, and extends in a direction. Another set of reinforcing projections is provided on a top surface of the lower plate and extended in another direction intersecting with the former direction.    USE - Power supply apparatus for a vehicle.    ADVANTAGE - The apparatus utilizes a vehicle body frame to be placed in spaces formed under the reinforcing projections, which provide a positioning guide when the apparatus is mounted on a vehicle body to permit the position of the support plate to be lowered while avoiding the interferences of the vehicle body frame with the lower plate, thus reducing a vertical space for mounting the apparatus in the vehicle body. The battery module is secured to the other reinforcing projections so as to eliminate need for special unit for securing the battery module. The apparatus allows cooling air in cooling spaces to flow uniformly and smoothly along bottom surfaces of the battery modules, thus enhancing cooling effect of the apparatus. The apparatus utilizes a provision of third reinforcing projections on a battery cover so as to ensure effective use of the top surface of the support plate, thus facilitating mounting of the battery module of the apparatus. The battery cover is coupled to the support plate to define an accommodation space to accommodate the battery modules so as to protect the battery module from damage caused by dust, water or collision with another object, and to allow the support plate and the battery cover to reinforce with each other, thus improving rigidity of the apparatus.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective view of a power supply apparatus for a vehicle.    Support plate (11)    Battery module (12)    Battery cover (13)    Lower plate (14)    Flat body (14a)    Cooling-air outlet opening (14h)    Upper plate (15)    Reinforcing rib (25)