The invention discloses a corn thresher. The corn thresher comprises a box cover arranged on the top of a box base. A feeding opening is formed in one end of the top of the box cover, a threshing rotary roller is rotationally connected into the box base and comprises a rotary shaft, a filter plate is fixed to the portion below the rotary shaft, the filter plate is inclined downwards from one end of the feeding opening to the other end of the feeding opening, a baffle is arranged at the bottom of the tail end of the filter plate, a corn stalk discharging opening is formed between the baffle and the end of the box base, and a corn kernel discharging opening is formed in the bottom of the filter plate. By the adoption of the structure of the corn thresher, cobs are threshed through a throwing rod, when the throwing rod just makes contact with corn, the corn can be threshed effectively; due to clearance fit of the throwing rod and a threshing rod, after the throwing rod makes contact with the corn, corn kernels left on the cobs are prevented from being damaged by the throwing rod, threshing efficiency is high, and the threshing effect is good; in addition, the threshed corn kernels and corn stalks are discharged from different side faces of the corn thresher, and therefore classified material collection is facilitated.