The invention discloses a corn thresher which belongs to the technical field of threshing machinery. The corn thresher comprises a feed hopper, a threshing device and a rack, wherein a feed port is arranged on the feed hopper, the threshing device comprises a threshing roller, threshing ribs are arranged on the threshing roller, a housing is arranged at the periphery of the threshing roller, a space for accommodating corns to be threshed is formed between the threshing roller and the housing, the housing consists of an upper housing and a lower housing which are movably connected with each other, the upper housing is connected with a discharge port, a suction fan is arranged on the rack, and a sieve is arranged at the exhaust opening of the suction fan and faces the threshing roller. The corn thresher is not provided with a power unit, thereby being small in size and simple in structure; and the price of the corn thresher is low, thereby being beneficial to the popularization of the corn thresher.