Abstract: An object of the invention is to provide a sealing device having a function capable of a plurality of tubular members such as plug tubes or the like being inserted side by side for sealing. In a sealing device (1) attached in an opening portion (2a) of a housing (2) for sealing between the housing (2) and tubular members (3) inserted to the opening portion (2a) of the housing (2), the sealing device (1) integrally has a mounting portion (4) fixed to the housing (2), seal lips (6) brought into close contact with outer peripheral surfaces (3a) of the tubular members (3) and following deformation portions (7) provided between the mounting portion (4) and the seal lips (6). The mounting portion (4) has a plurality of tubular inner surfaces (5), in which the tubular members (3) are inserted within a flat surface. Further, a plurality of the seal lips (6) and the following deformation portions (7) are provided in correspondence to the respective tubular inner surfaces (5).