A communication device for pipes of an air conditioner disclosed herein transmits and receives communication signals using induced electromagnetic force, generated by a signal line wound around a core assembly, thereby facilitating for coupling between the core assembly and the signal line. Also, one type of core assembly can be commonly applied to various standards of pipes. Rainwater or foreign materials cannot permeate between the signal line and the core assembly by winding the signal line on the core assembly, despite of external installation, thus preventing breakdown or degraded communication performance of the communication device. Also, with forming a signal line mounting hole through the core assembly, the signal line is fixedly inserted through the signal line mounting hole, thereby preventing in advance a movement of the core assembly even though a refrigerant pipe vibrates.