A sliding cover 30 includes an outside plate 70, a structural member 80 fixed to the rear face of the outside plate, a movable holding member 90 disposed in a space between the outside plate and the structural member, and toggling means 100 disposed between the holding member and the outside plate or the structural member. The holding member includes two parallel racks 82a and 82b, and guiding portions 81 disposed at both end portions and extending in the same direction as the racks. The holding member includes a holding plate 91; an even number of pinions 92a and 92b meshed with each other and supported by the holding plate so as to be rotatable; and guiding components 93 supported by the holding plate, the even number of pinions being disposed between the guiding components. The pinions located at both ends are meshed with the racks, and the guiding components are engaged with the guiding portions so as to be slidable. The biasing direction in which the toggling means biases the holding member is reversed substantially at the midpoint of the movable range of the holding member.