An air conditioning apparatus includes an air conditioning housing and a mode door. The air conditioning housing has a discharge chamber through which conditioned air is discharged out of the air conditioning housing. The discharge chamber includes a defrost vent, a main vent, floor vents and a rear seat vent. The floor vents are formed on opposite sides of a rear portion of the air conditioning housing. The rear seat vent is formed between the floor vents. The mode door has a front opening hole which is formed in a front portion of the mode door, a pair of main opening holes which are formed in a rear portion of the mode door at positions spaced apart from each other, and a rear-end opening hole which is formed behind a first portion provided between the main opening holes.