In order to produce metallurgical grade silicon and solar cell grade polysilicon in batches, a method of the present invention comprises: a step of reduction in an arc furnace, consisting of removing C and CO in a silicon reduction atmosphere using silica stone and carbon black by an arc so as to produce metallurgical grade silicon; a step of refining by slag consisting of removing phosphorus (P) and boron (B) by slag; a step of refining by unidirectional solidification consisting of removing metal impurities (Fe, Al, Ti, Mn, etc.) by means of unidirectional solidification; and a step of steam plasma-electromagnetism continuous refining consisting of charging a furnace with the unidirectionally solidified silicon and removing boron (B) by a steam plasma torch.