The invention discloses a gear grinding device. The gear grinding device comprises a platform, a motor, and a gear fixing seat; the motor and the gear fixing seat are separately fixed on the platform,the center of the gear fixing seat is provided with two-stage step holes comprising a first step hole and a second step hole, transmission shafts are arranged in the two-stage step holes, the transmission shafts are two-step step shafts comprising first step shafts and second step shafts, and the first step shafts are at the same height as a motor shaft. The gear grinding device is simple in structure and easy to machine, and materials can be easily obtained; through grinding, gears used in pairs can be well matched to avoid the problems of noise and transmission precision caused by matchingproblem; and at the same time, gears with different sizes can be grinded by the gear grinding device, and the utilization rate of the gear grinding device is enhanced.