Disclosed herein are single-layer and double-layer tablets, which release aceclofenac in a controlledmanner so as to achieve ideal drug release close to a straight line. Also, the tablets promote drug absorption in the stomach by controlling pH, contain aceclofenac with improved stability and haveboth immediate-release properties and sustained-release properties. Specifically, provided is an aceclofenac sustained-release tablet which is composed of an immediate-release layer containing aceclofenac, a water-soluble additive, a pH-controlling agent, a disintegrant, a filler and a lubricant and of a sustained-release layer containing aceclofenac, a release-controlling polymer, an oil-soluble surfactant, a filler and a lubricant, wherein the pH-controlling agent is sodium hydrogen carbonate, and the release-controlling polymer is a mixture of hydroxypropylmethylcellulose and carbomer.