A new beam-shaping device was realized by an abrupt taper with a length of $\sim 700\mu \mathrm{m}$ and a waist of $\sim 40\mu \mathrm{m}$ . The insertion loss of the device is less than 3%. The diameter of the flat beam top can be up to $\sim 900\mu \mathrm{m}$ with a small intensity variation (4%) and a small half-divergence angle (2.5°). The conversion efficiency of the new device from a Gaussian-shaped to a flat-top profile is comparable with that of a long-period-gratings-based device, while keeping the fabrication cost low. The new device requires only a fusion splicer and standard SMF-28 fiber, eliminating the need for photolithographic procedures. The new device also has no obvious incident light polarization dependence.