Proton pump inhibitors (PPIs) are used to treat acid-related disorders such as peptic ulcer and gastroesophageal reflux disease. Recently, vonoprazan, a novel potassium-competitive acid blocker (P-CAB), has been introduced as more effective treatment option. The purpose of this study was to clarify the adverse events associated with vonoprazan compared to PPIs using a spontaneous reporting system database. We performed a retrospective pharmacovigilance disproportionality analysis using the Japanese Adverse Drug Event Report (JADER) database. Adverse event reports submitted to the Pharmaceuticals and Medical Devices Agency between 2004 and 2017 were analyzed, and the reporting odds ratio (ROR) and 95% confidence interval (CI) for each adverse event were calculated. The database comprised 11,433 reports associated with PPIs, and 636 reports with vonoprazan. Hepatic and skin disorders were commonly detected in both PPIs and vonoprazan. There was a significant association of interstitial lung disease with PPIs as a class (ROR: 1.61, 95%CI: 1.47-1.77), but not with vonoprazan. Vonoprazan was strongly associated with haemorrhagic enterocolitis (ROR, 86.5; 95%CI, 59.7125). Among the PPIs, the signal score of microscopic colitis was noteworthy in the case of lansoprazole (ROR, 405; 95%CI, 348-472). It is suggested that there is a diversity in the strength of the association between PPIs and vonoprazan with adverse events. Our results may provide useful information for the treatment of acid-related disorders, but further research with more data is needed to finally clarify this.