PURPOSE: To prevent the harmful effects of heat as much as possible and improve comfortability and the like by forming an air lead-in port at a bonnet, and disposing a cooling unit between the air lead-in port and an engine unit in such a way as to allow air flow after passing the cooling unit to be led into a space part between a dash lower panel and the engine unit

CONSTITUTION: A bonnet 4 is disposed with comparatively steep inclination at the upper opening 19a of an engine room 19, and an air lead-in port 40 provided with plural louvers is formed in the position, opposed to the upper part of an engine unit 10, of the bonnet 4. A cooling unit disposed between the air lead-in port 40 and the upper part of the engine unit 10 is slightly inclined to the vehicle body rear side so that the axis of the cooling unit is placed closer to a ventilation flue 21 side, and a cowling 8 for deflecting the blown-off air flow forcibly toward the ventilation flue 21 side is mounted onto the first fan 6 side.