The sleep situations of Japanese children have serious appearances. The purpose of this study was to examine the effects of “visualization” practice concerning children’s sleep. Children in practical group recorded their own bedtime, wake-up time, sleep problems, steps per day, and the axillary temperature during practice period, and tried to plot the “visualization” index measurement. This study comprised surveys 1 and 2. The practice period was 4 weekdays and the participants were fourth-grade children in public elementary schools in both surveys. Survey 1 included 873 children from 8 schools in Tokyo. Of these, seven schools were practical group and one school was control group. Results of survey 1 reveal significant interactions between bedtime and wake-up time before and after practice in those with sleep problems and those without sleep problems at the practical groups. However, their effect sizes were small. Furthermore, in the results of reviewing the impressions after practice, many descriptions of “walking” and “steps” were found, so directing more attention to steps showed the possibility of effective improvement of children’s sleep situation. On the other hand, participants in survey 2 were 798 children from 7 schools in Tokyo. Of these, two schools were practical group and 5 schools were control group. It was found that those who had sleep problems at the practical group had significantly earlier bedtime and wake-up time at survey 2 . In addition, the sleep problems of those who had them before the practice decreased significantly after the practice, and it was confirmed that the steps per day increased in both, those with and without sleep problems before practice. Besides, the results of reviewing the impressions after practice revealed many descriptions of not only “walking” and “steps,” but also those connected with “physical condition” and “change”. Taken together, the practice in survey 2, advanced the bedtime and wake-up time of those who had sleep problems and reduced the sleep problems. From the above facts, it was concluded that the “visualization” practice concerning sleep, in which children themselves can know, feel, and think about their own body rather than acquiring knowledge about sleep, was a sustainable and effective to improve sleep situations among children.