Provided is a water jet spray nozzle, a water jet spray device, a gastrointestinal tract cleaning device, and a gastric wall cleaning device, whereby the cleaning performance with respect to water pressure can be increased, and when used to clean the gastric wall, gastric mucus can be effectively removed without damaging stomach tissue such as the gastric mucosa. A water jet spray nozzle (11) comprising: a flow path (11a) that includes, in order toward the distal end, a small-diameter portion (21) having an inner diameter that decreases from the upstream side, an expanded portion (22) having an inner diameter larger than that of the small-diameter portion (21), and a jet orifice (23) having an inner diameter smaller than that of the expanded portion (22). When water flows at a pressure of 0.2 to 0.6 MPa to the flow path (11a), the water collects in the expanded portion (22) and a cavitation bubble is generated heading from the small-diameter portion (21) toward the expanded portion (22). The inner diameter of the small-diameter portion (21) is 0.5 to 0.7 mm, and the inner diameter of the jet orifice (23) is 1 to 1.3 times larger than the inner diameter of the small-diameter portion (21).Linvention concerne une buse de pulvérisation à jet deau, un dispositif de pulvérisation à jet deau, un dispositif de nettoyage de tractus gastro-intestinal, un dispositif de nettoyage de paroi gastrique, permettant daméliorer les performances de nettoyage en termes de pression deau, et lors dune utilisation pour nettoyer la paroi gastrique, de supprimer efficacement le mucus gastrique sans endommager les tissus de lestomac, comme la muqueuse gastrique. Ladite buse de pulvérisation à jet deau (11) comprend : un trajet découlement (11a) qui comprend, dans lordre jusquà lextrémité distale, une partie à faible diamètre (21) dont le diamètre interne décroît à partir du côté amont, une partie à expansion (22) qui présente un diamètre interne supérieur à ladite partie à faible diamètre (21
