A low rigidity region being more stretchable and bendable than a high rigidity region, includes a main portion, and a medial first flexible portion and a lateral first flexible portion extending from the main portion in the medial and lateral directions. The main portion covers a portion of the area from the shaft of the first proximal phalanx to the shaft of the second proximal phalanx, the medial first flexible portion covers a portion of the area from the shaft of the first proximal phalanx to the head of the first metatarsal bone, and the lateral first flexible portion extends to the lateral side of the foot from the main portion. When pushing off the foot onto the medial/lateral side in a diagonally forward direction, the upper bends along the diagonal bend lines. Therefore, the diagonal portions and the main portion serve as the bend lines.