To avoid an arcuate rack or the like provided to decelerate the opening or closing motion of a lid when the lid is opened from being seen.

In a lid opening/closing device, the lid 4 is provided pivotably to a front panel 3 via rotary shafts 9, 10, and a means for decelerating the opening/closing motion of the lid 4 is provided. The arcuate rack 16 is provided inside of the front panel 3 on the rotary shafts 9, 10, the lid 4 is provided with a pinion 13 engaging with the rack 16 via an arm 5, thus forming the decelerating means.