A coffee grinder, in particular for the installation in a fully-automatic coffee machine, including an electric drive motor (1) for driving a grinding unit, wherein a reduction gear (4) formed as a planetary gear is arranged between drive motor (1) and grinding unit, with the sun gear (3) of this planetary gear being drivable by the drive motor (1). The planetary gear includes multiple planetary rods (8) arranged in the circumferential direction around the sun gear (3), these rods including a first axial portion (7) meshing with the sun gear (3) as well as an axially neighboring, second axial portion (9) with a second diameter different from, preferably smaller than, a first diameter of the first axial portion (7), with this second axial portion meshing with a stationary ring gear (11). The toothed racks are arranged to drive an output element (15) with their first axial portions (7).