This invention includes: an obstacle detection unit 400 that detects obstacles present around the working machine, by use of an image acquired by a camera 13; a position calculating unit 500 that calculates positions of each of the detected obstacles; a hazard zone calculating unit 700 that calculates a hazard zone based upon an attitude and motion of the working machine; a determining unit 800 that determines whether further obstacles are present in the calculated hazard zone; a risk level setting unit 2000 that sets a contact risk level for each of any obstacles present in the hazard zone; an image generating unit 600 that converts the camera image into a bird's-eye image centering upon the working machine, and then generates an image inclusive of all elements of the working machine and hazard zone on the bird's-eye image by further imaging the bird's-eye image diagonally from above an obstacle for which the highest contact risk level has been set by the risk level setting unit; and a display device 1300 that displays the generated image.This configuration makes an operator instantly recognize a position of the most potentially hazardous obstacle relative to the working machine, and thus improves working efficiency of the machine.