To realize the favorable operability of an opening and closing unit.

On an equipment body, a scanner unit 2 is rotatably provided and a gas spring and a torsion spring 2 energizing the scanner unit 2 to its opening direction are provided. By controlling the torsional angle range of the torsion bar 4 to the turning angle of the scanner unit 2 under the condition that the guiding rail surface 6, along which the top 10 of the arm part 4a of the torsion bar 4 and the shape of which has a predetermined one, of a guiding rail member 5, the total energizing force of the gas spring and the torsion bar 4 is made to be nearly uniform over the whole range of the traveling course between the opening position and the closing position of the scanner unit 2.