A device is designed to anchor a tissue to a bone. The device comprises a contractible implant, one or more sutures attached to the implant, and a pasty medicine capable of solidification. The implant is made of a flexible wall and provided with a holding portion and an injection port. The flexible wall is provided with a plurality of pores, each having a diameter smaller than 0.1 millimeter. The pasty medicine is injected into the holding portion of the implant upon completion of insertion of the contracted implant into the bone, thereby resulting in expansion of the contracted implant. The implant is thus securely lodged in the bone upon solidification of the pasty medicine to facilitate the anchoring of the tissue to the bone by suturing.