To provide a medical instrument and a method for regenerating biological tissue by which stimulations for regenerating biological tissue are applied to cells easily and speedily.

The medical instrument 10 comprises a plurality of fine needles 11 and a support 12 that supports each proximal end 14 of the fine needles 11 so as to arrange the plurality of fine needles 11 in an almost parallel fashion. The proximal ends 15 of the plurality of fine needles 11 are supported by the support and arranged in an almost parallel fashion. Each distal end of the plurality of fine needles 11 thus turns almost in the same direction. When in use, the plurality of fine needles 11 faces as a whole a desired biological tissue by holding the support 12. By bringing the support 12 close to the biological tissue, the fine needles 11 pierce the biological tissue almost simultaneously.