A guidewire (1) includes a core shaft (10) and a coil (20). The core shaft (10) has a diameter that decreases from a proximal end portion (11) toward a distal end portion (12), and the coil (20) is wound around an outer periphery of the distal end portion (12). The distal end portion (12) includes a most distal end portion (13) that is positioned at a most distal end of the distal end portion (12), and an intermediate portion (14) that is connected to the most distal end portion (13). The cross-sectional shape of the most distal end portion (13) is a rectangular shape. The cross-sectional shape of the intermediate portion (14) gradually changes from the rectangular shape to a circular shape in a direction from the most distal end portion (13) toward the proximal end portion (11). The length (X1) of the most distal end portion (13) is shorter than the length (X2) of the intermediate portion (14).
