Disclosed is a working machine that computes and displays moment by moment its dynamic stability and its state of contact with a ground in view of an inertia force and an external force applied to the working machine. Specifically, a working machine is provided with an undercarriage, a working machine main body mounted on the undercarriage, a front working mechanism attached pivotally in an up-and-down direction to the working machine main body, and a working attachment connected to a free end of the front working mechanism. The working machine includes a ZMP computing means for calculating coordinates of a ZMP by using position information, acceleration information and external force information on respective movable portions of the main body, which includes the front working mechanism, and undercarriage, and a stability computing means for calculating a support polygon formed by plural ground points of the working machine with a ground, and, when the ZMP is included in a warning region formed inside a perimeter of the support polygon, producing a tipping warning sound. The ZMP and the support polygon, which includes the warning region, is computed, and a display or warning is produced.