An air conditioner performs startup control in which compressor capacity is reduced as measured indoor temperature approaches a set temperature. A desired time of day is set directly or indirectly. A startup control apparatus of the air conditioner measures an inflection point occurrence time from when the air conditioner starts operation until when measured indoor temperature exhibits an inflection point. Alternatively, the startup control apparatus measures a control parameter lowering arrival time from when the air conditioner starts operation until when a control parameter transmitted to the compressor decreases to a prescribed value. A scheduled operation start time of the air conditioner is set as a time of day that is the desired time of day set moved forward by the inflection point occurrence time or the control parameter lowering arrival time. Operation of the air conditioner is started when the scheduled operation start time arrives.