A robot mower that automatically performs an operation in an operation area, the robot mower comprising: a mowing blade; a moving direction determination means configured to determine a moving direction of the robot mower; an image analysis means configured to extract a marker included in an image captured by a camera provided on the robot mower; and a survey means configured to acquire, by triangulation using a first point and a second point that the robot mower passes through during a movement in a constant direction, position information of the marker extracted by the image analysis means, characterized in that the moving direction determination means is configured to determine the moving direction, such that the robot mower moving in the moving direction does not come into contact with the marker and an angle (θg) between the moving direction and a direction from a current position of the robot mower to the marker is smaller than 45°, and wherein the survey means is configured to determine the first point (10-A) and the second point (10-B) during the movement of the robot mower in the moving direction such that an angle difference between: - a first angle (θA), which is the angle difference between the moving direction and the direction from the first point (10-A) to the marker, and - a second angle (θB), which is the angle difference between the moving direction and the direction from the second point (10-B) to the marker becomes close to 90°, the survey means being further configured to determine the first angle (θA) to be of about 45° and the second angle (θB) to be of about 135°. a mowing blade; a moving direction determination means configured to determine a moving direction of the robot mower; an image analysis means configured to extract a marker included in an image captured by a camera provided on the robot mower; and a survey means configured to acquire, by triangulation using a first point and a second point that the robot mower passes through during a movement in a constant direction, position information of the marker extracted by the image analysis means, characterized in that the moving direction determination means is configured to determine the moving direction, such that the robot mower moving in the moving direction does not come into contact with the marker and an angle (θg) between the moving direction and a direction from a current position of the robot mower to the marker is smaller than 45°, and wherein the survey means is configured to determine the first point (10-A) and the second point (10-B) during the movement of the robot mower in the moving direction such that an angle difference between: - a first angle (θA), which is the angle difference between the moving direction and the direction from the first point (10-A) to the marker, and - a second angle (θB), which is the angle difference between the moving direction and the direction from the second point (10-B) to the marker becomes close to 90°, - a first angle (θA), which is the angle difference between the moving direction and the direction from the first point (10-A) to the marker, and - a second angle (θB), which is the angle difference between the moving direction and the direction from the second point (10-B) to the marker becomes close to 90°,