A pepper mill includes a housing holding a driving mechanism and an output shaft, a top cover shell covered on the housing and defining with the housing a peppercorn chamber, the top cover shell having a peppercorn inlet through which peppercorns are inserted into the peppercorn chamber for further grinding, a threaded top neck, and a transparent swivel frame adapted to close/open the peppercorn inlet, a grinding mechanism provided in the top cover shell and driven by the output shaft to grind peppercorns into powder, a screw cap threaded onto the threaded top neck of the housing for output of ground pepper powder, and a protective cap adapted to close the screw cap.