An air conditioning apparatus for a seat of a vehicle includes a seat air-blowing unit disposed in a lower portion of the seat, and a seat duct for blowing air from an air conditioning unit to the seat air-blowing unit. The air conditioning unit includes a case for forming therein a cool air passage and a warm air passage, and a switching door for opening and closing the cool air passage and the warm air passage. When a stationary state is set from a cool-down state during cooling mode, the switching door closes the cool air passage to fully open the warm air passage. Thus, inside air is introduced into the warm air passage from a foot air outlet of the air conditioning unit, is supplied to the seat air-blowing unit through the seat duct, and is blown from a seat surface of the seat toward a passenger seated on the seat. As a result, in the air conditioning apparatus, cool air and inside air can be readily switched with a simple structure.