A grain sorting apparatus includes a conveyor belt mechanism for conveying grains, fed by a feed mechanism onto a conveying surface separately from each other at an upstream region with respect to a conveying direction, to a downstream end so that the grains are discriminated and sorted by a discriminating mechanism and a sorting mechanism when dropping from the downstream end along a predetermined path, the belt mechanism being disposed so that the conveying surface thereof declines as going downstream with respect to the conveying direction to prevent the grains being carried by the belt mechanism from rolling toward the upstream direction on the conveying surface of the belt mechanism. It is therefore possible to prevent the grains from rolling on the conveying surface of the conveyor belt mechanism toward the upstream direction relative to the conveying surface of the conveyor belt even when a conveying velocity of the conveyor belt mechanism is high.