A slab geometry Nd:YAG laser with a zigzag optical path is described. The dimensions of the Nd:YAG slab are 5.6 x 18.4 x 153.9 mm, and Nei' ion concentration is 1.1 at.%. Two krypton flashlamps, one located on each side of the YAG slab, are used for pumping. The conditions for normal pulsed operation were as follows: the repetition rate was from 5 to 27 pps, and the pulse durations were 4 and 9.9 ms. With the above conditions, a maximum average output power of 500 W was obtained with an efficiency of 2 %, the slope efficiency being 2.4 %. The beam divergence was estimated to be 10x25 mrad. The stability of the laser output power was about ±1.5 %. Another oscillator that includes intra-cavity cylindrical lenses, was also designed. Using this resonator configuration reduced the beam divergence to about 7.6 x8.2 mrad. The preliminary laser processing experiment was attemped using this laser oscillator.