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 drawn with a whole cross sectional reduction ratio as 80%-97.6%. The core wire 2 and a helical spring body 3 are welded by a welding member 4. The welding member 4 is made of eutectic alloy having a melting temperature ranging from 180° C.-495° C. Upon welding the helical spring body 3 to the core wire 2 which is made of the stainless steel metal, the procedure prevents the medical guide wire 1 from sacrificing its mechanical strength by significantly reducing the thermal influence on the core wire 2 and the helical spring body 3.