A control device comprises a storage unit and a control unit. The storage unit stores: the initial position of a moving optical system for adjusting the beam diameter of a harmonic laser beam output from a wavelength conversion crystal; and the movement allowable range of the moving optical system, which is defined as a distance from the initial position. The control unit moves the position of the moving optical system so that a processing point output value that is an output value on an object to be processed by the harmonic laser beam becomes a first set value or more, determines whether the position of the moving optical system after the movement is within the movement allowable range or not, and, when the position of the moving optical system is outside the movement allowable range, outputs an instruction for moving the wavelength conversion crystal to the outside.