To fit an insert at an accurate position of concrete in a single operation by oneself from both sides of one end of a sheathing board and to prevent a positional shift and an inclination when concrete is placed.

This bolt insert 10 is provided with a stem 12 having a head 11, a protruded male screw 13, a fixing nut 14 screwed to the male screw 13 to position and fix it to a form inner face, a truncated conical skirt 15 having a large diameter and diameter shrinking notches on the fixing nut side and exteriorly coupled with the male screw, and a temporary tacking nut 16 temporarily tacking the skirt 15 to the male screw 13.