[OBJECT] To reduce an inconvenience that, when an image detector is fixed to an image detector holder through rubber cushions, the thickness of the image detector including the rubber cushions increases by an amount corresponding to the height of the rubber cushions.[SOLUTION] An image detector 1 has a housing 2 of protrusive sectional shape. A difference in thickness between a central portion and peripheral portions of the housing 2 is made shorter than the length of rubber cushions 3. A plurality of rubber cushions 3 are attached to two rectangular bottoms of the peripheral portions made thinner than the central portion. Through these rubber cushions 3, the image detector 1 is fixed to an image detector holder 4.
