To provide a compact air conditioner for a vehicle with excellent temperature control.

An evaporator 20 and an electric heater 30 are disposed in a casing 10 from upstream to downstream. The evaporator 20 is disposed to completely obstruct a passage 11 in the casing 10, so that all the air introduced in the casing 10 passes through the evaporator 20. The electric heater 30 is disposed to completely obstruct the passage 11 in the casing 10, so that all the air introduced in the casing 10 passes through the heater 30. The heater 30 has two independent heating areas 31, 32 with different sizes. A differential outlet 40, a vent outlet 50, and a foot outlet 60 are provided downstream of the casing 10. These outlets 40 to 60 are opened and closed by open/close doors 41, 51, 61 respectively. The open/close doors 41 to 61 are opened/closed by 1 chip microcomputer, and power is supplied to the heating areas 31, 32 according to the mode and stored-program controlled.