The invention is related to a kind of device inside a grinder to peel the inner embryo membrane of coffee beans. It mainly comprises of a motor with an extruded motor shaft, a positioning cylinder located on the lateral side of a motor and equipping a lower exit inside an conveyor base, and a conveyor base, which is on the lateral side of the grinder and equips an extruded exit end on the other side of the grinder. The center of the motor extrudes a shaft connecting an eccentric synchronic rotation grinding bar. During rotation, the shaft is in a state of eccentricity, thus, the grinding surface completely hits the inner ring rim of the positioning cylinder and coffee beans are ground into particles. There is an inclined conveyor platform on the conveyor base. When grinding particles fall, due to low specific weight, the embryo membrane is sucked by a fan located on the lateral wall of a grinder and is collected in a dust collection bag. The particles not sucked out fall along the inclined conveyor platform on the conveyor base into a material collection bag. After grinding, the separation of coffee particles and the membrane is fully achieved.
