The survey system includes a mobile body equipped with a scanner configured to perform scanning by a distance measuring light, a position measuring device configured to measure a position of the scanner, and a posture detecting device configured to detect a posture of the scanner, the posture detecting device includes an imaging unit configured to periodically acquire image data, a 3-axis angular velocity sensor configured to detect 3-axis posture angles of the scanner, and an arithmetic control unit, and the arithmetic control unit is configured to calculate posture information of the scanner by summing photographing-time 3-axis posture angles (SP0, SP1, SPn) of the scanner acquired in each photographing by image analysis of the image data, and 3-axis posture relative displacement angles of the scanner calculated from detection values of the 3-axis angular velocity sensor.