The present study is to examine the attention improvements of young children with developmental delays who have difficulty in attention by applying tone and rhythmic activity. The subjects were three young children attending an E nursery for only children with disabilities, and the tone and rhythmic activity was progressed with total 26 times for 8 weeks, that is, 2-3 times a week, and the activity was carried out for 20 minutes each time. In the present study, the attention behavior evaluation scale of Conners was rated before and after the tone and rhythmic activity so as to find an attention improvement degree of the children. Also, it was analyzed about how attention was changed through video observation by using behavior observation sheets, and the number of attention was measured in an interval of 30 seconds each time. The result of the present study is as follows. First, the tone and rhythmic activity made eye contact of the young children with developmental delays. Second, the tone and rhythmic activity increased activity participation and order observance of the young children with developmental delays. Third, the tone and rhythmic activity was effective in decreasing inappropriate sound of the young children with developmental delays. Fourth, the attention increased through the tone and rhythmic activity and the decrease of inappropriate sound was maintained even after mediation was completed. Accordingly, if we do research/develop and use a program for the tone and rhythmic activity designed and applied to be suitable to characteristics of the young children with developmental delays, it could give positive effects to attention improvement as well as decrease of problematic behavior of the young children with developmental delays.