The utility model relates to a reciprocating rocking device of a bearing internal grinder, which is characterized in that the utility model comprises an AC servo motor (1) with an encoder (2), wherein the output shaft of the AC servo motor is connected with a rocking shaft (3), and a bearing seat and a pressing plate are fixedly connected with a supporting plate seat (10) through bolts; the upper end of the rocking shaft is movably connected with a wheel disc (5), the upper part of the wheel disc is provided with a handwheel adjusting mechanism (4), and the wheel disc is connected with a piston connecting rod of a reciprocating oil cylinder (7) through a connecting plate (6); a reciprocating supporting plate is supported by cross roller guide rails which are arranged on the supporting plate seat, and a drive motor of a grinding wheel is fixed on the reciprocating supporting plate. The utility model can simplify the machining of an eccentric shaft, an eccentric sleeve is cancelled, the cost of the reciprocating rocking device can be reduced wholly, requirements of high speed grinding can be satisfied and the surface quality and the grinding efficiency of grinding work pieces can be improved.