A laser surveying system, comprising a light source for emitting a laser beam, a projection optical system for turning the laser beam from the light source to a parallel luminous flux, a scanning unit for projecting the luminous flux of the projected laser beam for scanning, a scanning direction detecting unit for detecting a scanning direction, a photodetection optical system for receiving a reflected light of the projected laser beam from an object to be measured, a photodetection element for performing photo-electric conversion of the reflected light received via the photodetection optical system, and a distance measuring unit for measuring a distance based on a signal from the photodetection element, wherein the projection optical system has a luminous flux diameter changing means, and a luminous flux diameter of the projected laser beam is enabled to be changed.