In the study of animal behavior, “personality” is defined as a consistent individual differences in behavior. Over the past decade, studies of animal personality have received much attention and have been reported in a wide range of taxa, but mainly in mammals and avians. Personality is assumed to be formed by interaction between inherent factors (genetic or maternal effects) and environmental factors (experiences or surrounding conditions). However, there are few studies investigating the effects of environmental factors, especially from the developmental perspective. I studied personality of a parthenogenetic gecko, Lepidodactylus lugubris, which clone populations are known to live in the wild. Genetically identical animals are ideal for investigating the developmental aspect of personality. I collected geckos in the field and experimentally evaluated boldness and exploration in the laboratory. To investigate the presence of personality, I first examined whether behavior is consistent across contexts (contextual generality) and through time (repeatability). I found individuals with various boldness among the population, and the same individuals maintained consistent bold tendencies over contexts and time. The occurrence of behavioral variation among individuals and the consistency within individuals indicated that clone geckos have personality. Next I investigated the development of personality. Generally, individuals experiences more things as they grow, thus it can be assumed that personality variation among individuals becomes greater throughout growth. I defined four growth stages based on body size of geckos and compared boldness variation among them. In the youngest stage most individuals showed high boldness score, and personality variation was low. On the other hand, in other older stages there were various individuals, from bold to shy ones, and therefore personality variation was high. This result suggests that personality variation among individuals increases throughout growth.