For minimally-invasive therapy for spinal canal stenosis, a therapeutic device capable of stationing an interspinous process spacer without the need of large skin incision or ligamentous tissue incision and also without the need of detaching of the paraspinal muscle from the spine. The interspinous process spacer includes a conoid screw region (2) to be screwed into a processus spinosus interspace; a spacer region (3) in the longitudinal direction of the screw region (2); head region (4) capable of free interlocking with a tool arbitrarily; and through-hole (5) passing through the axial centers of screw region (2), spacer region (3) and head region (4). The processus spinosus interspace is enlarged by screwing of the screw region (2) into the processus spinosus interspace. The spacer region (3) is pinched upon passing of the screw region (2) through the processus spinosus interspace to attain enlarging and fixing of adjacent processus spinosus interspaces.