An air conditioner comprises a freezing cycle circuit, which includes, successively provided on a main duct line 11 in the mentioned order, a compressor 10, a four-way valve 12, an external heat exchanger 13, a pressure reducer 14, and an internal heat exchanger 11, the main duct line 11 branching into at least an upper and a lower part coolant flow line 20 and 30 in the internal heat exchanger 15, and an on-off valve 10 provided on the upper part coolant flow line 20 and closed in a low capacity cooling operation. The air conditioner can gently cool and gently dry air in a room without causing chillness to be felt.