Marine protected areas (MPAs) are considered an effective tool for protecting marine organisms. The precise estimation of home range size, as well as diel differences in home ranges, are essential when considering the appropriate size of an MPA. In addition, behavioral characteristics of spawning migration should also be considered for species that form spawning aggregations. Our aim was to clarify the diel variation in home range size and the degree of precision of the returning ability of white-streaked grouper Epinephelus onus by acoustic telemetry. Seventeen individuals were studied, and nighttime home range sizes that were calculated by 50 and 95% kernel utilization distributions were 5.9-fold and 5.5-fold greater, respectively, than the daytime home ranges. The average inter-center distance between home ranges during the 2 time periods ranged from 3.0 to 67.9 m (22.5 m on average), suggesting that the day-night home range shift within the home ground varied individually. Returning ability for 10 individuals that showed clear spawning migration behavior was also analyzed, and the average inter-center distance between home ranges during the periods before and after spawning was 8.1 m. Eight out of these 10 individuals showed precise returning after the spawning migration to the patchy coral substrates that were used before the spawning migration. The present study suggests that appropriate setting position of the home ground can establish long-term protection of the species due to their precise returning ability after the spawning migration.