PURPOSE: To make a copper wire easy to pass through a catheter main body so as to secure a smooth flow of blood inside a blood vessel into which the catheter main body is inserted by extruding the catheter main body to cover the copper wire, and forming the catheter main body with an almost elliptical cross section.

CONSTITUTION: A copper wire 8 and the copper wire 10 and the constantan wire 11 of a thermocouple sensor are fed into a die 15 located at the end of an extruder 14 and a resin material supplied from a supply opening 14A is fed into the die 15 in a melt state and is extruded therefrom, so as to mold a pipe-shaped body P through extrusion in which the copper wire 8 serving as a catheter main body 1 and the copper wire 10 and the constantan wire 11 of the thermocouple sensor are embedded; the cross section of the catheter main body 1 is roughly elliptical. Thus embedding of the copper wire 8 is achieved simultaneous with extrusion molding of the catheter main body 1, so the manufacture of a balloon catheter is facilitated. Also the cross-sectional area of the catheter main body 1 can be reduced and a smooth flow of blood can be secured since a gap 22 forms in a place near the center position of the blood vessel H.