Objectives : The purpose of the study is to investigate the risk factors of dental caries in early childhood. Methods : Subjects were 197 mothers having 5 year old children. They completed the questionnaire from June 1 to July 14, 2012. Results : At birth, the age of mother and the number of teeth experiencing dental caries showed high correlation(r=0.163, p<0.05). Early beginning(r=-0.441, p<0.05) and long period(r=0.441, p<0.05) of mix feeding were closely related to dental caries outbreak. Long period of supplementary food caused deciduous dental caries (r=0.643, p<0.001) and dental caries experience (r=0.723, p<0.001). Long period of breast feeding (r=0.261, p<0.001) also caused deciduous dental caries. Low BMI of mother was colsely related to high dental caries(r=-0.206, p<0.01). Deciduous dental caries accounted for 61.8% and the number of teeth experiencing dental caries was 68.5%. Conclusions : Appropriate breast feeding habit is the most important behavior of preventing deciduous dental caries in 5 year old children.