Laser beam machine and method for controlling laser beam machine

A laser beam machine includes: a laser oscillator that outputs laser light; a transmission fiber through which the laser light output from the laser oscillator propagates; a first adjuster that is disposed between the laser oscillator and an incidence end of the transmission fiber and changes an incidence numerical aperture of the laser light incident to the incidence end of the transmission fiber; a second adjuster that converges the laser light and changes a zoom magnification of the laser light between an emission end of the transmission fiber and a workpiece; and a controller that performs adjustment of a beam diameter of the laser light at an image forming position of the laser light and adjustment of an emission numerical aperture of the laser light emitted from the emission end of the transmission fiber independently of each other, by changing the incidence numerical aperture.