Purpose The purpose of this investigation was to identify developmental score of children with cerebral palsy for six months using Korea Bayley Scale of Infants Development. Methods The participants were 23 children who were diagnosed to cerebral palsy and ages ranged between 12 months and 42 months. We assessed motor ability using GMFCS at first time and we obtained developmental scores of KBSID3 for twice times during 6 months. We analyzed developmental scores of Korea Bayley Scale of Infant Development between 1st and 2nd in six months by paired t test, we compared each section scores of KBSID according age, gestation periods and duration between 1st and 2nd six months using by ANCOVA. Results There was significantly difference of each section scale score of cognition, receptive language, fine motor, gross motor, social emotion between 1st and 2nd of six months in all participants and we could see significantly difference of section composite scores of cognition and motor between 1st and 2nd of six months in all participants(p<.05). The indices of KBSID and GMFCS are significantly negative correlated(p<.05). Conclusion As a result of the followup study of children with cerebral palsy for six month using by BSID, there was significantly difference of cognition sections and motor sections depend on gestational period. Language , social emotional and adaptive behavior sections showed different results in scale scores and composite score, but depending on are showed significantly differences in adaptive behavior section.