In a medical guide wire (1), a flexible core wire (2) is made of austenitic stainless steel wire treated with a solid solution procedure, and tightly drawn with a whole cross sectional reduction ratio as 90%-99%. Upon forming a head plug (41) at a distal end by welding a distal end tip of the core wire (2) to a distal end tip of a helical spring body (3), a eutectic alloy is used as a welding member (4). The eutectic alloy has a predetermined melting temperature point so as to reduce a thermal influence against the core wire (2), thereby improving a mechanical strength property of the core wire (2) so as to lengthwisely reduce and diametrically minimize the head plug (41).
