Sleep disorders are a major social problem that prevails in modern society, and urgent action is desired. Currently, many supplements that are supposed to improve the sleeping environment are on the market. However, the effect is extremely weak compared to the prescription. It is well-known fact that conventional sleep studies have observed a decrease in core body temperature from the time of falling asleep, but it has been verified that the core body temperature from the time of falling asleep is actively raised by ingesting ice slurry to lead to falling asleep. In this study, 11 people, mainly university students, ingested ice slurry before falling asleep, and examined whether the quality of sleep was improved by the ratio of non-REM sleep time due to the decrease in core body temperature. We recorded the situation in which the quality such as temperature and humidity and sleep time was comprehensively evaluated in each sleep environment of the subjects. Comparing the presence or absence of ice slurry before falling asleep, there was a tendency that the deep sleep time was longer when ingested. Therefore, it was suggested that the decrease in core body temperature due to ice slurry improves the quality of sleep.