A telescopic cover has a plurality of cover pieces nested in the order of their size for extension and retraction. A rubber cushion is on a side surface of an end portion of an insert-side cover piece, a wiper is inside an upper surface of a receiving-side cover piece receiving the insert-side cover piece so as to contact the upper surface of the insert-side cover piece, and a stopper is on the inner side surface of the end portion so as to be offset from the position of the wiper and face the rubber cushion. When the telescopic cover is retracted so that the respective end surfaces of the receiving-side and insert-side cover pieces become flush with each other, a gap between the cover pieces is closed by the wiper.