A seat air-conditioning system for automotive vehicles includes an air-conditioning unit for generating cold air or hot air, a driver seat including a seat portion provided with a plurality of air discharge holes through which to discharge the cold air or the hot air to the outside, a front passenger seat including a seat portion provided with a plurality of air discharge holes through which to discharge the cold air or the hot air to the outside, an outlet duct mounted to the air-conditioning unit for drawing the cold air or the hot air from the air-conditioning unit therethrough, a seat duct connected to the outlet duct for supplying the cold air or the hot air to the driver seat and the front passenger seat therethrough, and a seat blower attached to the outlet duct for blowing the cold air or the hot air at an increased flow rate.