The invention discloses a corn thresher, which comprises a feed hopper, a threshing device and a bracket, wherein the feed hopper is arranged on the upper part of the threshing device; the threshing device is fixed on the bracket; a discharge outlet is arranged at the lower end of the threshing device; the threshing device consists of a threshing drum, a pressing plate and a baffle plate; the pressing plate is positioned above the threshing drum and is arc-shaped; the baffle plate is positioned on the side face of the threshing drum and the pressing plate; an arc-shaped threshing bin is enclosed by the threshing drum, the pressing plate and the baffle plate; the inlet end of the threshing bin is bigger than the outlet end of the threshing bin in caliber; threshing tendons or threshing teeth are arranged on the threshing bin; a protecting shell is arranged at the bottom of the threshing drum; the pressing plate consists of a pressing plate, a pressing tube, a pressing strip and a pressure spring; and an elastic device is arranged on the top of the pressing plate. The corn thresher solves the problems of feeding and threshing corn cobs with different sizes, can feed and thresh in batches, is good in threshing effect and high in threshing speed, has a threshing rate of nearly 100 percent, and is simple in structure and low in both production cost and use cost.