To provide an air conditioner for a vehicle which enhances a fitting property even if it has a hot air guide passage for inhibiting generation of a cool defrosting phenomenon.

A defroster blowing out opening 22 and a foot blowing out opening 23 are arranged in parallel and when the foot mode is selected by a rotary door 20, a part of hot air approaching to the foot blowing out opening 23 is introduced from an inlet hole 30a opened by an auxiliary communication hole 20e and is guided to the defroster blowing out opening 22 side. Since the inlet hole 30a is provided against the foot blowing out opening 23 in adjacent to the defroster blowing out opening 22 side, a passage forming part of the hot air guide passage 30 is integrally formed with an air conditioning case.