Abstract: A flangless winding core for magnetic tape is adapted for stacking between like winding cores. The core has an annular body with top and bottom annular body surfaces, an outer circumferential surface to wind the tape thereabout, and an inner circumferential surface from which each of a plurality of equidistant projections with high and low circular extensions extends in the outward directions of the top and bottom annular body surfaces and a like plurality of recesses with two circular notches in the both edges thereof and corresponding to the high and low circular extensions are arranged in a space adjacent to the projections, so that the recesses can be consequently corresponded to the projections at the time of stacking the cores.