Abstract: A surveying instrument includes a sighting telescope optical system, a distance measuring system which outputs first data, a phase detection autofocus system which and outputs second data, and an AF driver which moves a focusing lens of the sighting telescope optical system to bring the sighting object into focus in accordance with one of the first data and the second data. A surveying instrument is also disclosed, which includes a sighting telescope and an AF drive unit which is provided separately from the sighting telescope, wherein the AF drive unit can be mounted to and dismounted from a body of the surveying instrument.