Areas 11—1a, being in contact with an O-ring 13, of an outer peripheral surface of a taking lens 11—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—1 in a section taken along a plane including the optical axis. The O-ring 13 is disposed in contact with the areas 11—1a and 12a, which are formed in the taper shapes, of both of the outer peripheral surface of the taking lens 11—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—1 and the inner surface of the lens frame 12.