A mounting device is provided having a base, first mounting arms, second mounting arms, first engaging portions, and second engaging portions. The base is annular and has an elastic body. Both first and second mounting arms have elastic bodies and extend from said base in the outward radial direction of said base. The first engaging portions project orthogonally to the axis of said base from the edge of said first mounting arms. The second engaging portions project in the direction opposite to the projection direction of said first engaging portions, from the edge of said second mounting arms. The first engaging portions project parallel to each other in the same direction.