The invention relates to a conveying mechanism of a vibrating screen, in particular to a simple amplitude-adjustable vibrator. The simple amplitude-adjustable vibrator comprises a fixing rack, a plate body, an adjusting lug, a first fastening rod, a second fastening rod, a roller and a driven rod, wherein an annular groove is formed in the plate body; the first fastening rod and the second fastening rod are fixed in the annular groove; one end of the adjusting lug is hinged to the first fastening rod; an arc chute is formed in the other end of the adjusting lug; the second fastening rod penetrates through the arc chute and is fixedly connected with the arc chute through a nut; the circle center of the arc chute is positioned on the first fastening rod; the roller is propped against the side surface of the plate body, is positioned above the plate body, and is connected with the driven rod; and the driven rod is slidably connected to the fixing rack. In order to solve the problem that the stroke of an existing vibrating screen cannot be debugged so that the existing vibrating screen cannot adapt to various types of seeds, the stroke-adjustable vibrating screen is provided.