Abstract
This study investigated the effects co-sleeping at night has on children's attachment to parents and self-esteem, then examined how and until when co-sleeping should be done. A questionnaire survey was taken by 424 undergraduate and graduate students. As a result of analysis of variance, men who have the experience of co-sleeping and those who were lying next to their mother have a higher score of AMBIVALENT measure, although it is a tendency. And although it is a tendency, it was found that who stopped co-sleeping at up to 0-3 years old and those who stopped co-sleeping after being 6 years old have a higher score of AVOIDANT measure. About self-esteem, a sufficient result was not obtained. Among SECURE measure, AMBIVALENT measure and AVOIDANT measure sex differences appeared in the score. Though not related to the experience of co-sleeping, men have a higher score of SECURE measure than women, women have a higher score of AMBIVALENT measure than men, and men have a higher score of AVOIDANT measure than women.