Different kinds of adaptive opportunities are selected in bedrooms, such as air conditioning and natural ventilation; however, the thermal environment created by these measures is not necessarily good for sleep. In this research, a field survey was carried out to investigate the effect of the total thermal environment and its variation on sleep. First, we investigated the effect of airflow and found that an increase in air turbulence causes an increase in the duration of wakefulness. Next, we adjusted the comfort equation for sleep and calculated the thermal load on the body and its variation. We found that both negative and positive increase in the heat load on the body causes an increase in the probability of awakening. An increase in its variation also resulted in an increase in the probability of awakening. We concluded that when planning a pleasant thermal environment for sleep, it is important to consider the total thermal environment and to take into account the effect of its variation as potential cause of sleep disruption.