To provide a multi-chamber air conditioner wherein intermittent refrigerant flow noise in an expanding mechanism in an indoor unit is reduced or prevented, regardless of the change of a weather condition, an installation condition and an operating condition.

This air conditioner is provided with a rectifying device wherein an enlarged pipe part having a diameter larger than a diameter of inlet-side piping is formed on the inlet-side piping of the expanding mechanism, a refrigerant transmitting member through which the refrigerant is transmitted, is mounted on the enlarged pipe part. A refrigerant passing area of the refrigerant transmitting member and front and rear parts of the refrigerant transmitting member is larger than the refrigerant passing area in the inlet-side piping.