A display system of a working machine includes: a tilt sensor that detects a pitch angle and a roll angle of a working machine; a calculation unit that calculates a tilting position on polar coordinates that indicates a magnitude and a direction of tilt of the working machine based on the detected pitch angle and roll angle; a display unit that displays various kinds of information; a display processing unit that displays, on a predetermined region on a display screen of the display unit, a monitor-displayed level that performs a polar coordinate display of the tilting position and a marked line indicating a preset magnitude of tilt; and a setting processing unit that performs a setting to change display content of the monitor-displayed level.