PURPOSE:To recondition the used casting sand to be one similar to the new casting sand by using a centrifugal friction type casting sand reconditioning equipment and a grinder polishing type casting sand reconditioning equipment as a coarse and fine reconditioning equipment respectively in a combined manner. CONSTITUTION:When the used casting sand is reconditioned, a dry centrifugal friction type casting sand reconditioning equipment 1 as a coarse reconditioning equipment of the casting sand, and successively, a dry grindstone grinding type casting sand reconditioning equipment 11 as a fine reconditioning equipment are used in a combined manner. For example, the used casting sand is continuously reconditioned at the rate of 3t/hour by the centrifugal friction type casting sand reconditioning equipment 1. When the batch finishing reconditioning of this reconditioned sand is executed by the grindstone grinding type casting sand reconditioning equipment for 25 minutes, the increase of SiO2, reduction of acid consumption and reduction of the ignition loss can be obtained. Thus, the baked carbide and the clay layer adhered to the sand grain surface can be ground and separated, and the casting sand in the condition close to the new one can be reconditioned, the projecting part of sand grain is removed, and the grain shape is improved to be round.