PURPOSE: To provide an air conditioner capable of preventing dew condensation from occurring on an air blowing fan during cooling operation under the frosting condition by leaving no gaps between each of fins of a plurality of upper- and lower-staged heat exchangers and each of side plates provided on both sides of the fins.

CONSTITUTION: An air conditioner has a plurality of upper- and lower-staged heat exchangers 3 and an air blowing fan 4, each being provided in an air passage connecting inlet ports 2 to an outlet port 5, which are formed in a main body 1 of the air conditioner. Accordingly, each heat exchanger 3 comprises a number of plate-like fins 3a, which are arranged in substantially parallel with one another at predetermined intervals and causes an air stream to flow through each gap between the fins 3a, each side plate 3c, which has a projection 3d projecting inwardly in its upper stage or in its lower stage, has insertion holes and is provided on both sides of the fins 3a, and heat transfer tubes 3b, which extend at right angles with the fins 3a and communicate to the insertion holes of the side plates 3c, whose respective both ends are connected to a plurality of U-shaped pipes 3e and which cause a fluid to flow through their interiors.