<p>This invention discloses a flame retardant thermoplastic polyurethane resin composition containing a halogen flame retardant and a flame-retardant, water-resistant thin insulated wire prepared by applying the flame retardant thermoplastic polyurethane resin composition to a conductor (21) to form an insulating layer (22) having a thickness of 0.3 mm or less. The flame retardant thermoplastic polyurethane resin composition is prepared such that 0.2 to 20 parts by weight of a cycloparaffinic compound having an epoxy group is added to 100 parts by weight of a thermoplastic polyurethane resin alone or contained as a major constituent in a thermoplastic resin.</p>