A multiple-unit oral sustained release preparation is provided which allows controlled release of imidafenacin [4-(2-methyl-1-imidazolyl)-2,2-diphenylbutylamide]. The preparation serves to ensure a prolonged effect of imidafenacin and prevent rapid elevation in the blood levels of imidafenacin.Specifically, granules or powders comprising imidafenacin dispersed in a water-insoluble polymer or a higher alcohol are used in the preparation. These preparations achieve sustained release of imidafenacin since the molecular network structure that the water-insoluble polymer or the higher alcohol forms during the preparation of the granules or powders serves to control the rate of diffusion of imidafenacin in water. Granules comprising a core granule having two layers of an inner imidafenacin coating and an outer water-insoluble polymer coating are used in the preparation. The water-insoluble polymer coating serves to control the rate of diffusion of imidafenacin in water and ensure sustained release of imidafenacin. The multiple-unit oral sustained release preparation is provided in the forms of capsules and tablets containing the granules or powders that allow controlled release of imidafenacin. The preparation achieves controlled release of imidafenacin over a prolonged period of time.