Background of Study: Oral health is the part of the body's health that can not be separated from one another, especially at preschool children who are in an important period in the development of physical and psychological. The problem of tooth caries experienced by 85% of children under 5 years in Indonesia, one of the reason is the habit of drinking milk bottle at the end of the age of five. Caries can be severer when children are given a bottle of milk as a bedtime because saliva production during sleep is so slow that make swallow reflex lower lowering and then the last suction before the child fell sleep will make a pool in the mouth and in contact with the teeth for hours. Aim of Research: The aim of this research is to find out the relationship between bottle feeding as a bedtime and dental caries severity level in 4-6 years old children. Research Methodology: This is an analytic observational research with cross sectional design. The sample was taken with total sampling technique to 72 kindergartners. Caries severity level measured with Caries Severity Index (CSI) examination. The data analysis was using independent t test. Research Result: The result shows that the 18 kindergartners consumed bottle feeding as a bedtime, while the 54 kindergartners are not consumed bottle feeding as a bedtime. The average caries severity level in kindergartners with bottle feeding as a bedtime is 2.69 while who are not consumed bottle feeding as a bedtime is 1.97. There is a relation between bottle feeding as a bedtime with dental caries severity level in 4-6 years old children in Kasihan, Bantul. Conclusion: There is a relation between bottle feeding as a bedtime with dental caries severity level in 4-6 years old children in Kasihan, Bantul.