Air conditioner

The invention provides an air conditioner, which aims at continually performing heating operation after operation prevention during frosting. In order to achieve the aim, the air conditioner is provided with: a shunting return circuit connecting a discharge side of a compressor with an inlet side during heating operation of an outdoor heat exchanger; a shunting electromagnetic valve performing on/off of the shunting return circuit; and a control device controlling rotating speed of the compressor and the shunting electromagnetic valve, the air conditioner, via the control device, under the condition of determining whether possible frosting is generated on the outdoor heat exchanger during heating operation, and when a state of possible frosting is changed to an impossible frosting, reduces rotating speed of the compressor, and cuts off the shunting return circuit after the rotating speed reaches a predetermined value.