Areas 11.sub.--1a, being in contact with an O-ring 13, of an outer peripheral surface of a taking lens 11.sub.--1 and an area 12a, being in contact with the O-ring 13, of an inner surface of a lens frame 12 are formed in taper shapes having slopes with respect to an optical axis of the taking lens 11.sub.--1 in a section taken along a plane including the optical axis. The O-ring 13 is disposed in contact with the areas 11.sub.--1a and 12a, which are formed in the taper shapes, of both of the outer peripheral surface of the taking lens 11.sub.--1 and the inner surface of the lens frame 12. Also, the O-ring 13 is pressed in directions of arrows P and P' by the outer peripheral surface of the taking lens 11.sub.--1 and the inner surface of the lens frame 12.