A surgical instrument having including a fixed handle and a pivoting handle, an elongated treatment part operating rod connected to the pivoting handle which advances and retracts with the operation of the pivoting handle, an insertion part through which the operating rod is inserted, a pivoting base supported on the distal end portion of the insertion part via a pivoting shaft so that the pivoting base is free to pivot, an elongated pivoting base operating rod whose distal end portion is connected to the pivoting base which causes the pivoting base to pivot about the pivoting shaft, a treatment part base which is connected to the pivoting base, and on which a surgical treatment part which performs an opening-and-closing action is disposed, and a joint member having a plurality of universal joints connects the treatment part operating rod and the surgical treatment part disposed on the treatment part base.