When a working condition is set, if an operator sets the working condition, a control device (1) obtains an expected load factor of a laser oscillator (2) based on the set working condition, and displays the load factor as a working condition check bar (8) on a display device (3). The operator adjusts the working condition so that a load factor of the laser oscillator (2) stays within a predetermined range while watching the working condition check bar (8) and determines an appropriate working condition. Therefore, it is possible to prevent excessive load from being applied to the laser oscillator (2) at the time of actual working.