To enable one to stand firmly on tiptoe for strengthening the entire feet by giving a fifth toe potion a shape that allows it to touch ground earlier than a first toe portion by making the thickness of the toe portion thinner in the first toe portion of a shoe sole than the fifth toe portion.

By making the thickness of the toe side 2 of a shoe sole 1 thinner in a first toe portion than a fifth toe portion, the toe portion is shaped so as to make the first toe portion touch ground earlier than the fifth toe portion when one stands firmly on tiptoe. Basically, the part below the distal phalanx, the proximal phalanx, and the metatarsal bone of the first toe is made thin. However, depending on the extent or degree of motion, that part changes. The larger the difference in thickness between the first toe portion and the fifth toe portion of the sole 1 of foot strengthening footwear, the greater the force applied to the toe potion. Therefore, desirable thickness is about 10 mm at a maximum. With the foot strengthening footwear on, one can stand firmly on tiptoe during walking or running and can strengthen his feed. The foot strengthening footwear has great practical value such as suitability to volume production due to a simple structure and availability to users at a low cost.