In an object positioning and fixing device that positions and fixes a work pallet on a base member: a reference seating surface is formed on the base member; a contacting surface is formed on the work pallet; fitting cylindrical portions of a plurality of reference members are fixed in a plurality of fitting holes in the base member; a plurality of annular engagement members are installed in the work pallet; each of the reference members has an engagement projection; a base end contacting surface of the base end of the engagement projection is brought into contact with the reference seating surface so as to set the height position of the engagement projection; and the annular engagement member engaged over the outside of the engagement projection is elastically deformed in the radially outward direction so that it tightly contacts against the tapered engagement surface.