The present invention is to provide a sustained release preparation comprising a drug-containing core substance and a multilayered coating layer covering the core substance, wherein all adjacent layers in the multilayered coating layer contain mutually different hydrophobic organic compound-water-soluble polymer mixtures; and, a method of producing a sustained release preparation, having a multilayered coating layer in which adjacent layers contain different hydrophobic organic compound-water-soluble polymer mixtures, which comprises spray-coating a solution containing a hydrophobic organic compound-water-soluble polymer mixture onto a drug-containing core substance, continuing to spray-coat a solution containing a different hydrophobic organic compound-water-soluble polymer mixture onto the resulting coating layer, and repeating this step.