To adopt a belt slide method even in conveying heavy load by disposing a pressurization-type compression spring capable of adding pressure in advance on a lower surface of a flexible slide plate, and uniformizing the distribution of pressure.

In a pressurizing spring mechanism, a base plate 9 is horizontally fixed on the upper surface of a base 8 made of a square steel pipe, the shafts 10, 11 are uprightly stood on both sides of the base plate 9, and the pressurizing springs 12, 13 are wound on these shafts. An upper surface plate 14 is supported by the pressurizing springs 12, 13, and vertically moved while guided by the shafts 10, 11. A flexible slide plate 5 is placed on this upper surface plate 14, and a stopper plate 16 for preventing the displacement in the advance direction, of a pressing plate 14 preventing the lateral displacement of the flexible slide plate 5, is fixed thereon. The pressurizing spring mechanisms are mounted along a convey belt at proper intervals.