Physical activity (PA) is associated with reductions in the risk of all-cause mortality and in the prevalence of cardiovascular disease and stroke. Nevertheless, a large proportion of the general population may not be sufficiently active. PA level has been reported to be influenced by genetic factors, and we investigated whether Q223R polymorphism in the leptin receptor (LEPR) gene was associated with PA level. A total of 556 Japanese adults aged 24 - 65 years old participated in this cross-sectional study. The duration and intensity of PA were objectively evaluated by triaxial accelerometry. Q223R polymorphism was determined by the TaqMan method. The distribution of Q223R polymorphism was: QQ 0.7%, QR 22.6%, and RR 76.6%. The relation between the LEPR genotype and PA level was analyzed by ANCOVA with age and sex as covariates in the Q dominant genetic model. There were significant differences between LEPR genotypes and the time spent in light PA or inactive time. The subjects with RR genotype showed significantly shorter time spent in light PA (RR genotype: 559.4 ± 102.9 min/day, QQ/QR genotype: 579.9 ± 103.1 min/day) and longer inactive time (RR genotype: 815.5 ± 107.5 min/day, QQ/QR genotype: 792.3 ± 107.7 min/day) than the subjects with QQ/QR genotype (P < 0.05). There were no such differences in the time spent in moderate or vigorous PA. These results suggest that the variety of PA level, especially spontaneous PA in humans, is partly caused by diversity in the LEPR gene.