A spiral unit includes a base tube extended along a longitudinal axis and made of a first thermoplastic resin, and a fin disposed on an outer peripheral surface of the base tube along a fin axis spirally extended around the longitudinal axis and made of a second thermoplastic resin. The fin includes a strip portion provided in a state of being bonded to the outer peripheral surface of the base tube and spirally extended along the fin axis. The second resin being mixed with a magnetic material in the strip portion.
