The present study examined whether Go/Nogo reaction time (RT) is a relevant index of the sport expertise relating to sport-specific decision-making. 57 male university students, 20 basketball players, 24 baseball players, and 13 sedentary students as a control group, performed a Simple RT task and Go/NoGo RT task which had baseball specific stimulus-response relations. Participants in baseball and basketball differed further in having high, medium, and low experience in the sports. For comparisons across sports, the basketball and the baseball players had significantly shorter reaction times than the nonathletes in both tasks. In contrast, reaction times varied significantly across experience for the baseball players in the Go/NoGo RT task but not for basketball players. These results suggested that Go/NoGo RT could be used as an index of expertise for sport-specific decision-making, if stimulus-response relation in Go/NoGo RT task has a natural relation for a particular sport-domain.