A polishing device includes a reducer, a polishing mechanism, a rotatably driven mechanism, and a sliding driving mechanism. The polishing mechanism is connected to the reducer. The rotatably driven mechanism includes a first driving member and a transmission shaft, the first driving member includes a first main body and an output shaft rotatably connected to first main body, the transmission shaft is fixed to the output shaft. Sliding driving mechanism includes a second driving member, the second driving member includes a second main body and a driving shaft collar connected to the second main body, the second main body is fixed to the first main body. The second main body and driving shaft collar cooperatively define a through hole. The transmission shaft extends through the through hole and is connected to the reducer to enable the polishing mechanism to polish a workpiece. The driving shaft is fixed to the reducer.