A primary technical goal of a mechanical seal device of the present invention is to decrease assembly cost thereof as well as machining cost thereof and to prevent wear of seal surfaces by preventing occurrence of squealing noises of the seal surfaces. The mechanical seal device comprises a first seal ring which is one of a pair of seal rings and disposes an engagement portion at the outer circumferential surface, a retainer ring which has a first support portion supporting an inner diameter surface of the first seal ring and a second support portion engaging the engagement portion and is fixed with either a seal housing or a shaft, and a gasket which joins the retainer ring and the first seal ring in a sealing manner, wherein an engagement clearance (C) formed in a rotational direction between the engagement portion and the second support portion is within 0.5 mm.