A heat exchanger mounted in an air conditioner is constructed such that at least one row of heat conduction pipe groups are arranged across an air passage. Each heat conduction pipe group is constructed such that a plurality of heat conduction pipes 22 are arranged in parallel with each other and a fine wire 23 made of a metallic material having excellent heat conductivity is spirally wound around each adjacent heat conduction pipe 22. Thus, performances of the heat exchanger can be improved without a possibility that the air conditioner is designed with larger dimensions. In addition, the heat exchanger includes a plurality of heat conduction pipes 39 arranged in the form of at least one row with a constant distance between adjacent ones and a plurality of twisted wires 40. The twisted wires 40 are arranged so as to alternately come in contact with one side and opposite side of each heat conduction pipe 39 extending at a right angle relative to the row direction of each heat conduction pipe 39, and moreover, alternately come in contact with one side and opposite other side of each heat conduction pipe 39 extending in the longitudinal direction. With this construction, high heat conductivity can be realized, and an occurrence of clogging with condensation can be prevented while improving heat conduction.