To provide excellent usability without the mulfunction of operation switches even if strong pressure is applied to a shielding body by providing a plate having a large opening part and a small opening part, a fitting member for fixing the plate and a holding body integrally to each other, and a clearance holding member for forming a specified clearance between the plate and the holding body.

A shielding body 11 is provided between an operating cover and a holding body. This shielding body 11 is provided with a plate 12 having a large opening part 13 and the like large enough for an operator to insert the finger to operate a first control switch, and a small opening part 14 and the like through which the operator cannot insert the finger so as not to be able to operate a second control switch. The distance between the plate 12 and the holding body is kept almost constant by fitting members 15, 15a and a clearance holding member 16. Accordingly, even when the surface of the plate 12 is pressed to the holding body 8 side by the finger in the opened state of the operating cover, there is no mulfunction of the first control switch and second control switch due to being pressed by the back face of the plate 12.