A prosthetic foot structure comprises a mounting case, a first curved flexible member, a second curved flexible member, an upper block, a lower block, and an elastic body. The first curved flexible member defines an opening. A plurality of bolts are provided for affixing the first curved flexible member to the mounting case. The second curved flexible member extends through the opening of the first curved flexible member in a direction generally opposite to the first curved flexible member. The upper block and the lower block are fastened together by a screw. The second curved flexible member is fastened to the lower block by bolts. The upper block, the lower block, and the second curved flexible member are mounted in the mounting case by a pin. The elastic body is placed against the second curved flexible member and snugly fitted in the opening of the first curved flexible member.