To provide a laser beam machining mechanism which can improve productivity by simultaneously irradiating a plurality of streets formed in parallel on the surface of a workpiece with laser beams.

The laser beam machining mechanism includes: a chuck table 36, a laser beam irradiation means 5; a machining feed means 37 which moves a chuck table 36 and the laser beam irradiation means 5 relatively in a machining feed direction; and a dividing feed means 38 which moves the chuck table 36 and the laser beam irradiation means 5 relatively in a dividing feed direction perpendicular to the machining feed direction. The laser beam irradiation means 5 includes: a laser beam oscillation means; a laser head 55 which is equipped with a plurality of objective condenser lenses 54 disposed at prescribed intervals and irradiates the workpiece with the laser beams emitted by the laser beam oscillation means through the plurality of the objective condenser lenses 54; and an an inter-optical axis distance adjusting means for adjusting the inter-optical axis distances in the dividing directions of the plurality of objective condenser lenses.