Abstract: A dust tight closed type belt conveyor for conveying dust contained materials to be scattered out during operation; which comprises the conveyor belt supported in a form of concave by a plurality of rollers and a plurality of glide plates and also the bulged cover roof closing the upside space over the conveyor belt, so that all make a dust tight and closed conveying space extending in the driving direction. Further, the belt conveyor is preferably provided with a system for avoiding the belt meandering motion causing a harder dust scattering.