To avoid reduction of effective cabin volume and shorten air conditioning piping by rationally arranging an air conditioner of an airplane.

A carry-through 12 integrally connecting spars 11 of left and right main wings WL and WR of the airplane is arranged below a fuselage F, and fairing 14 covering the carry-through 12 is protruded from a lower face of the fuselage F. The air conditioner C producing air for air-conditioning a cabin 13 by exchanging heat of high temperature bleed air extracted from an engine E provided on the main wings WL and WR with the low temperature atmosphere is arranged in a space 15 partitioned between the lower face of the fuselage F and the fairing 14. By this, large effective cabin volume can be secured and the piping of the air conditioner C can be shortened.