A guidewire (1) includes a core shaft (2) having a front end portion (2a) and a rear end portion (2b), a helical coil (3) in which the front end portion (2a) is inserted, and a solder part with which the front end portion (2a) and the helical coil (3) are bonded to each other. The helical coil (3) is formed of a wire (3a) having a plurality of grooves (3b) in a surface of the wire (3a), the grooves (3b) being formed such that more grooves (3b) are formed along the axial direction of the wire (3a) than along the circumferential direction of the wire (3a).
