The present invention provides a MOS-type variable capacitance element which can obtain a sufficient capacitance valuable width and, at the same time, can eliminate restrictions imposed on a control voltage range. A scanner may be used to read an identifier, such as a barcode, on a removable storage media. Accordingly, the fusing roller uses the heat pipe, thereby reducing warm-up time for initial operation. The plurality of pairs of wafers are each connected to a set of micro-machined parts. Upon rotation of the first rotary body, the valve flaps are in engagement with the boundary surface of the first rotation chamber and are rotated in mutually opposite directions with regard to the first rotary body so as to form two mutually demarcated working chambers within the first rotation chamber.