The utility model discloses an LC adapter and an optical transmission device, the LC adapter comprises a housing and a dustproof cover, one end of the housing is provided with a first accommodating groove, two opposite side walls of the first accommodating groove are provided with
lap joint projections, and one surface of the
lap joint projections facing the groove bottom of the first accommodating groove is set as a
lap joint surface; one end of the dustproof cover is rotationally mounted on the groove wall of the first containing groove, the outer side face of the dustproof cover abuts against the lap joint face, and the
peripheral side face of the dustproof cover is in clearance fit with the groove wall of the first containing groove; an assembling protrusion is formed on the portion, close to the rotating axis of the dustproof cover, of the lap joint face, an assembling concave part is arranged on the edge of the dustproof cover corresponding to the assembling protrusion, and the assembling protrusion is matched with the assembling concave part. In this way, the outer side face of the dustproof cover is attached to the lap joint protrusion, the
peripheral side face of the dustproof cover is attached to the groove wall of the first containing groove, external interference light and dust are difficult to enter the groove from a bending gap between the dustproof cover and the groove wall of the first containing groove, and the dustproof effect and the light blocking effect are better.