Abstract: The present invention relates to a coil structure, which provides a heating capacity not lower than a conventional heating capacity, reduces the work of a compressor, and executes double-stage condensation, and to a heat pump system which uses the coil structure and raises the temperature of heat as high as possible during condensation by executing first-stage compression and second-stage expansion. In the coil structure, a plurality of element tubes is connected to distribution conduits in parallel. When the coil is stood up, the element tubes are connected to each other in series to form five horizontal rows to one thousand horizontal rows of element tubes, and are connected to each other by the distribution conduits in parallel with each other to form a set of a single row or a set of two rows based on a vertical row.