The present invention relates to a round undulating blade for shredder, where a sheet metal is integrally formed into a round undulating blade to serve as the blades for constructing a blade module. The blade includes: a periphery; an undulating blade flank including at least two cambers having a first curvature and at least two cambers having a second curvature alternatively arranged with respect to the cambers having the first curvature; and hooked edges formed on the periphery of the cambers having the first curvature, wherein the undulating blade flank of the blade serves to cut paper along a longitudinal direction to form paper strips having double-tapering end, and the hooked edges serve to cut the strips along a horizontal direction into paper chips. These characteristics help to reduce the manufacturing cost, reduce the motor load and power consumption, to thereby enhance the market competitiveness.