A multi-purpose bolt unit for fixing an object to a drilled hole formed in a soft construction structure, the multi-purpose bolt unit comprising: a cylindrical body for insertion into the drilled hole of the soft construction structure; a front end tip formed at a lower end of the cylindrical body and having a larger outer diameter than an outer diameter of the cylindrical body; an upper thread surface formed in an upper side of the cylindrical body while spaced apart from the front end tip; an elastic packing pipe inserted into the cylindrical body and placed on the front end tip; an upper washer inserted into the cylindrical body and placed on an upper end of the elastic packing pipe; a compression nut screwed to the upper thread surface and pressurizing the upper washer so that the elastic packing pipe expands; and a fastening screw groove formed inside the cylindrical body and opened upward through the compression nut, wherein the compression nut comprises: a nut cap screwed to the upper thread surface to be spaced apart from an upper end of the cylindrical body; a cap through-hole formed in an upper side of the nut cap to expose the fastening screw groove; and a wrench groove formed in an upper side of the nut cap, exposing the cap through-hole, and suitable for having a wrench inserted therein not to be rotatable, wherein an inner diameter of the cap through-hole is larger than an inner diameter of the fastening screw groove and smaller than an inner diameter of the wrench groove. a cylindrical body for insertion into the drilled hole of the soft construction structure; a front end tip formed at a lower end of the cylindrical body and having a larger outer diameter than an outer diameter of the cylindrical body; an upper thread surface formed in an upper side of the cylindrical body while spaced apart from the front end tip; an elastic packing pipe inserted into the cylindrical body and placed on the front end tip; an upper washer inserted into the cylindrical body and placed on an upper end of the elastic packing pipe; a compression nut screwed to the upper thread surface and pressurizing the upper washer so that the elastic packing pipe expands; and a fastening screw groove formed inside the cylindrical body and opened upward through the compression nut, wherein the compression nut comprises: a nut cap screwed to the upper thread surface to be spaced apart from an upper end of the cylindrical body; a cap through-hole formed in an upper side of the nut cap to expose the fastening screw groove; and a wrench groove formed in an upper side of the nut cap, exposing the cap through-hole, and suitable for having a wrench inserted therein not to be rotatable, a nut cap screwed to the upper thread surface to be spaced apart from an upper end of the cylindrical body; a cap through-hole formed in an upper side of the nut cap to expose the fastening screw groove; and a wrench groove formed in an upper side of the nut cap, exposing the cap through-hole, and suitable for having a wrench inserted therein not to be rotatable, wherein an inner diameter of the cap through-hole is larger than an inner diameter of the fastening screw groove and smaller than an inner diameter of the wrench groove.