In melting and casting by a water-cooled crucible induction melting technique, a partition means is inserted on top portion of a melt, and a new raw material for is charged on an upper side of the partition means to continue the melting and casting. Therefore, the continuous casting can be kept while avoiding mixture of the melt on a lower side of with the melt on an upper side of the partition means. A partition plate or a partition plate with legs can be used as the partition means. When the present invention is applied to production of a silicon ingot used for a solar cell and the like, productivity is largely improved, which allows costs to be remarkably reduced in solar energy generation. Therefore, the present invention can widely be utilized as the method for casting a polycrystalline-silicon ingot for a solar cell.