A radial rotary dryer improves drying efficiency for sludge and other substances, prevents clogging phenomenon, and is realized in a simple structure. The radial rotary dryer includes spaces formed by inner and outer drums and partitioned by a plurality of radial plates . The substances, which have been introduced through a drum inlet together with hot blowing air, sequentially move throughout all spaces and are dried during drum rotation. The substances are discharged through an opposite side of the inner drum. A lift plate is attached at one surface of each radial plate to improve the drying efficiency. Hammers are attached to an opposite surface of the radial plate to free-fall according to the rotation of the drum, thereby crushing the substances. The radial rotary dryer is useful to dry sewage sludge, food waste, or other industrial substances with the best drying efficiency, the minimum installation space, and a crushing function.