To provide a high quality and low cost core material for a guide wire for medical treatment having excellent operability by having appropriate suppleness at an inserting part and by providing appropriate rigidity at a guiding part, and the guide wire for medical treatment.

In the core material, the inserting part has form adaptability, and the guiding part has torque transmittance. The inserting part 2 made of a TiNi wire material and the guiding part 3 made of a SUS304 wire material are integrally bonded at a connection part 4 made of a Ni foil.