Many studies have used event-related potential and neural oscillations to probe the underlying neural mechanisms of inhibitory control in adults, but little has been done in typically developing preschoolers. In this study we tested healthy preschool children between the ages of 5 and 6, and observed better response inhibition in 6-year-olds compared to 5-year-olds. Importantly, this age-related difference could not be explained by the N2 component from event-related potential, but was reflected in an increase in right frontal beta power from electroencephalogram. These results suggest that frontal beta power during the preschool period may reflect neural development of inhibitory control.