Abstract: A link mechanism capable of setting any desirable speed of opening/closing a lid during a series of the opening/closing operation and capable of exerting a strong driving force is provided. A lid 6 is attached to a lid bracket 31. The lid bracket 31 is pivotally connected to a driving lever 14 and a coupled-driving lever 15 with which the lid 6 is opened or closed. The driving lever 14 is provided with a cam having an elongated hole 34, into which a driving pin 36 provided to a sector gear 13 is fitted. The sector gear 12 is driven by a motor through a pinion 22. According to rotation of the sector gear 13, the driving pin 36 moves in the elongated hole 34 and drives the driving lever 14. Since the distance between the center of the sector gear 13 and the driving pin 36 is larger than the radius of the pinion 22, such mechanism exerts a strong driving force.