PROBLEM TO BE SOLVED: To provide a microbubble generation nozzle capable of improving the concentration of dissolved gas without reducing the cloudiness performance by adjusting to reduce the bubble diameter uniformly, and to increase the number density.SOLUTION: The microbubble generation nozzle 1 of a gas generator includes a plurality of decompression parts having a large-diameter part sandwiched between back and forth in series. Gas dissolved water is flowed from the large-diameter part at the inlet end to the large-diameter parts at the outlet end to generate bubbles in the decompression part. A flow passage of the gas dissolved water is shaped so that the pressure loss from the decompression part 111 on the upstream side to the large diameter part 102 is larger than the pressure loss from the decompression part 112 on the downstream side to the large diameter part 103.COPYRIGHT: (C)2013,JPO&INPIT【課題】気泡径を均一に小さく、数密度を増加させるように調整し、白濁性能を低下させずに溶存気体濃度を向上させることができる微細気泡生成ノズルを提供すること。【解決手段】太径部を前後に挟んだ減圧部を直列に複数備え、気体溶解水を入口端の太径部より出口端の太径部へと流して、減圧部で気泡を発生させる気体発生装置の微細気泡生成ノズル1であって、上流側の減圧部111から太径部102に至る間の圧力損失が下流側の減圧部112から太径部103に至る間の圧力損失より大きくなるように気体溶解水の流路の形状を形成したことを特徴とする。【選択図】図1