There is no established view of how gastric acid suppression affects the time for gastric emptying. Vonoprazan fumarate shows potent and durable gastric acid inhibitory effects, but its effects on gastric emptying have not been studied widely. We investigated the effects of vonoprazan fumarate on gastric emptying and measured serum gastrin and plasma ghrelin levels in healthy adults. Ten participants were administered 10mg vonoprazan fumarate daily for 14days, then 20mg vonoprazan fumarate daily for 14days. The gastric emptying breath test was performed and serum gastrin levels were measured at baseline and after each medication administration period. The protocol was then repeated, with the gastric emptying breath test and serum gastrin and plasma desacyl-ghrelin levels measured at baseline and the end of the medication trial. Mean serum gastrin levels increased in a dose-dependent manner [baseline: 104.7 ± 50.4, after 10mg protocol: 328 ± 123.8, after 20mg protocol: 555 ± 378.8 (pg/mL, mean ± standard deviation), p = 0.0008]. There was a significant difference between the gastric emptying breath test Tmax at baseline and just after the 20mg protocol (baseline: 45.5 ± 15.3, after 20mg protocol: 60.5 ± 19.6min, p = 0.0418). Plasma desacyl-ghrelin levels increased significantly just after the 20mg protocol compared to those at baseline [baseline: 222.3 ± 106.4, after 20mg protocol: 366.2 ± 178.6 (fmol/mL), p = 0.0008]. In healthy adults, 14days of vonoprazan fumarate administration at 20mg/day delayed gastric emptying. This clinical trial was registered in the University hospital Medical Information Network Clinical Trial Registry (Trial No. UMIN000039199 and UMIN000042969).