The utility model relates to a convex arc section idler for belt conveyer with wave-like flange which is mainly used for the guiding and bearing load of rubber belt, comprising a supporting base 4, a shaft 12, bearings8 and 10, a sleeve 11 and an end cap 5. The bearings8 and 10 are embedded in the inner cavities of the two ends of the sleeve 1, connected integrally with the sleeve 11. The sleeve 11 is positioned on the shaft 12, the two ends of the sleeve 11 is sealed by the end cap 5, and the two ends of the shaft 12 is positioned on the supporting base 4. The sleeve of the utility model rotate, but the shaft does not rotate, the force is mainly borne by the sleeve. For the diameter of the sleeve is bigger than the diameter of the shaft, the bearing force can be great, and synchronously, for the volume of a bearing seat is not limited, the diameter of the shaft can be enlarged according to the requirement of supporting force, which overcomes the defects that the shaft is easy to break and the bearing is easy to be damaged in original structure.