A geodetic apparatus, in particular tacheometer or theodolite, comprises an optical device for sighting objects, a first support on which the optical device is supported such that the optical device may turn around a first axis, and a first gear unit for transmitting a drive torque on the optical device so as to turn the optical device around the first axis. In thegeodetic apparatus, the first gear unit comprises a worm and a worm gear meshing with each other, wherein the worm has a plate-like body and a spirally extending worm thread is formed on a first side face of the body, and the worm gear has a plurality of teeth evenly distributed along a circle.