We have previously reported that Eriobotrya japonica seed extract (ESE) is effective for the treatment of various gastric mucosal injuries. For the pharmaceutical preparation of ESE, we are evaluating deep sea water (DSW), which contains trace elements and has a homeostasis-enhancing effect, as the solvent. In this study, we prepared DSW containing ESE (ESE + DSW) and evaluated its usefulness for the prevention of gastric mucosal injuries using non-steroidal anti-inflammatory drug-induced acute gastric mucosal injury models in male Wistar/ST rats. Gastric mucosal injury models were prepared by administering indomethacin at 30 mg/kg orally to the rats after a 24-h fast. ESE was prepared by a routine procedure and administered at the same concentration as in the administration to humans. The rats were divided into the following 6 groups: ESE, DSW, ESE + DSW, tap water (control), rebamipide (positive control), or untreated. Gastric mucosal injuries were evaluated by measuring the injury area, lipid peroxide (LPO) level, antioxidative enzyme level, and volume of mucus. The injury area and LPO levels in plasma and gastric tissue were significantly reduced in the ESE and ESE + DSW groups compared with the control and DSW group. The plasma and gastric tissue antioxidative enzyme levels were significantly higher in the ESE and ESE + DSW groups than in the control group. These results suggest that DSW, when combined with ESE, inhibits antioxidative enzymes, and enhances the gastric mucosal protecting effect of ESE.