Laser beam machine, laser beam machining method, and machining nozzle

This laser beam machine is provided with a machining nozzle (10) that causes the sending to a machining subject from an aperture section of: laser light (2A) used in laser beam machining; and an assist gas that is blown at the machining subject during laser beam machining. The machining nozzle (10) has dimensions such that when the focal point position of the laser beam (2A) has been moved, the aperture diameter of the aperture section is smaller than the beam diameter of the laser beam (2A) at any position of the aperture section, at least the position interfering with the laser light (2A) is formed from a material that is transparent to the laser light (2A), and thereby it is possible to easily have assist gas flow at a high flow speed.