The present invention relates to a simple and effective method for preparing a tamsulosin HCl sustained-release tablet and a tamsulosin HCl sustained-release tablet produced thereby. The method comprises the steps of: dissolving tamsulosin HCl as an active ingredient in an organic solvent; dissolving the tamsulosin HCl solution in hydroxypropylmethylcellulose phthalate to prepare a binder solution; and kneading the binder solution with a hydroxypropylmethylcellulose phthalate/glyceryl dibehenate mixture as an excipient and allows tamsulosin HCI to be released at uniformly controlled amounts in a subtained-release manner in vivo by controlling drug release rate according to different pH environments in vivo, so that it shows improved bioavailability and minimized side effects.