A calculation part calculates a maximum temperature reached which is reached by the coolant or component of each part, in the case of machining in accordance with laser machining conditions that were inputted or set, based on the cooling capacity of a chiller, tank volume of the chiller, heat generation amount from the laser oscillator, heat capacity of a cooled part of the laser device, etc. which are recorded in a recording part, and the temperature of each part measured by temperature detection parts, etc. In the case that the maximum temperature reached would exceed the allowed maximum temperature, a warning is made prior to starting laser machining.