This disclosure provides a device for heating to generate a uniform molten pool, including: a source unit for generating an energy beam; a beam expanding/reducing unit positioned in an energy path of the energy beam for adjusting the diameter of the energy beam; a flat-top conical lens set positioned in the energy path and including at least two flat-top axicons, with the beam expanding/reducing unit positioned between the source unit and the flat-top conical lens set; and a focusing lens positioned in the energy path, with the flat-top conical lens set between the beam expanding/reducing unit and the focusing lens, and the energy beam being focused by the focusing lens. This disclosure generates a uniform molten pool to prevent vaporization splash due to overheating of the material during melting.