An object of the present invention is to provide surgical instruments which can insert a block-shaped interspinous spacer into a space between adjacent spinous processes with easier operations. The surgical instruments of the present invention are instruments for inserting the interspinous spacer having a block-like shape formed with a hollow portion into the space between the adjacent spinous processes. The surgical instruments include an insertion instrument having an inserting portion adapted to be passed through the hollow portion of the interspinous spacer, and a grasping instrument for grasping the insertion instrument, wherein the insertion instrument and the grasping instrument are adapted to be used under the condition that the insertion instrument is inserted into the hollow portion of the interspinous spacer and in such a state the grasped portion of the insertion instrument which is provided near the first end of the insertion instrument is grasped by the grasping instrument. The insertion instrument is provided with a support portion for preventing the interspinous spacer from being fallen off from the insertion instrument when the insertion instrument is inserted into the hollow portion of the interspinous spacer, at the second end thereof which is the opposite end of the first end.