Disclosed is a method for manufacturing an electric wire, which can economically manufacture the wire having an air gap formed stably for an insulator covering a conductor and exhibiting good transmission efficiency. The circumference of a central conductor (12) that is drawn out from an insertion hole (44) formed in the center of a point (41) is covered with an insulator (13) consisting of resin(R) by extruding the resin (R) to annular extrusion channels (51, 52) consisting of the gap between a die (31) having a truncated conical inner circumferential surface (32) and the point (41) having a truncated conical outer circumferential surface thus manufacturing an electric wire (11). Three or more tubular bodies (45) extending through the extrusion channels (51, 52) along the extrusion direction are provided on the outer circumferential surface of the point (41) at equally-spaced intervals in the circumferential direction, and the resin (R) is extruded to the extrusion channels (51, 52) thus forming a plurality of air gaps (14) in the resin (R) continuously in the longitudinal direction, at intervals in the circumferential direction, by the air flowing from the tubular bodies (45).