To provide a control device capable of enlarging an allowable working range of a working machine by avoiding restriction of the rated performance of the working machine more than necessity by an overhanging width of an outrigger in a working machine with outriggers.

A working machine with a plurality of outriggers 111-114 includes: a working condition detecting means 1 for detecting the working condition of the working machine; an outrigger overhanging width detecting means 2 for detecting the overhanging width of each outrigger 111-114; an outrigger selecting means 6 for selecting a specified outrigger 114 having the minimum overhanging width; a minimum vertical distance output means 7 for computing the vertical distance S1 from the center of turn Q relative to a straight line R connecting a grounding point P4 of the specified outrigger 114 and a grounding point P3 of other outrigger 113 adjacent to the specified outrigger 114; and a rated performance computing means 5 for computing the rated performance under the present working condition based on the working condition and the minimum vertical distance.