Congenital Hypothyroidism is a condition of thyroid hormone de ciency since birth.The effects of congenital hypothyroidism are disruption of intellectual and cognitive function in children. Intellectual and cognitive disturbances in children with congenital hypothyroidism can be affected due to the low number of neurons in the brain. This research aims to determine the effects of walking exercise adequately to the number of neurons in rat cerebellar cortex of congenital hypothyroidism. Design is experimental, posttest control group design. Postes used to analyze differences in the number of neurons in the cortex the molecular layer cerebellum of mice in various groups. The subjects were holdingrats, Sprague Dawleyaged 4-5 months, healthy and ready to get pregnant. Parent pregnant required 12 were divided into 6 groups each 2 tail.4 group induced hypothyroidism with given prophilthiourasil (PTU), 2 normal group. Each child born mice were then grouped in accordance with the treatment that has been given to the mother. Data were obtained from observations of a numerical scale data. To test the hypothesis of a difference in all treatment groups used statistical analysis of One Way Anova. The number of neuron cells on average in the group as much as 177 cells Normal, Normal practice 209 cells, 152 cells PTU group, PTU group exercise 173 cells,153 cells Thyroxine group,group Thyroxine exercise 195 cells. Withanalysis One Way Anova obtained by value p = 0.004 (p-value <0.05). Adequate exercise brisk walking increases the number of neurons in rat cerebellar cortex molecular layer of congenital hypothyroidism.