The utility model relates to harvesting machinery for upright crops, and provides a rotary corn harvester to solve the technical problem that large-sized corn harvesters are unavailable for small plots. The rotary corn harvester comprises a frame, travelling wheels on the frame, and a belt pulley for transmitting power, a main drive gear on a belt pulley shaft is meshed with a change gear and another main drive gear on a drive shaft, and the drive shaft is in reversing drive with a tool shaft to drive a rotary cutting tool in rotation. The rotary corn harvester is simple and compact in structure, can be mounted at the front end of a small-sized tractor conveniently, and can be used for harvesting corn in all lands on which the small-sized tractor can be operated.