A beam generating apparatus includes a laser light source, a speckle suppressing module, a light homogenizing module and a driving unit. The laser light source outputs a laser beam. The speckle suppressing module includes two biconic lenses and a diffuser. The first biconic lens is disposed on a transmission path of the laser beam. The diffuser is located on the transmission path of the laser beam between the first and second biconic lenses. The light homogenizing module is disposed on the transmission path of the laser beam from the second biconic lens. The driving unit drives the diffuser to move with respect to the laser beam so that the ratio of the M2 of the laser beam exiting from the second biconic lens in a first direction to the M2 thereof in a second direction is greater than 2, wherein the two directions are substantially perpendicular to each other.