Abstract: To restrict bone absorption occurring as time elapses after osseous integration, a dental implant comprises an internal thread 1a; an external thread 1b having a largest crest diameter of a complete thread at the most intra-oral side; and a collar portion 1c provided on the intra-oral side of the external thread 1c to have diameters that expand from a portion including a root diameter of the complete thread of the external thread 1b at the most intra-oral side to a bellied portion having an approximately equal diameter to the crest diameter of the complete thread of the external thread at the most intra-oral side, and thereafter reduce to an intra-oral side of the collar 1c having an approximately equal diameter to the root diameter, wherein surfaces of the external thread 1b and side surfaces of the collar 1c are subjected to a surface roughening treatment.