This study is to investigate the change of sleep in daily life during the follicular and luteal phases of the menstrual cycle. The seven healthy women, subjects aged 19-47 years participated in this study for two days during sleep. The protocol was approved by the institutional ethics review committee. All participants gave their consent to this study. We examined the RR interval variability for two and a half hours from the onset of sleep. After the night experimental, Subjects answered the following questionnaire such as sleep onset latency, awaked time during sleep, subjective evaluation of the sleep by using visual analog scale. Autonomic function was estimated by the Lorenz plot and time domain for RR interval. The hours of sleep and sleep onset latency in the follicular and luteal phases was 359.1±80.5 min and 357.0±43.1 min, 25.4±10.3 min and 20.0±11.5 min, respectively. The RR interval during sleep was increased in the beginning, and decreased, and then increased again in both phases. The ultradian rhythm in the sleep cycle of RR interval in both the follicular and the luteal phase was 76.5±11.5 min and 72.8±8.0 min, and there was no significant difference during 2 hours and a half from the onset of sleep between both phases. The correlation between the subjective sleeping quality and hours of sleep was statistically significant (R=0.580, R2=0.336) in the luteal phase, but not in the follicular phase (R=0.208, R2=0.043). We concluded that although autonomic nervous activities during sleep, the subjective quality of sleep and hours of sleep did not show individually significant differences between the follicular and the luteal phases, the sensation score on sleep quality might be correlated with not only the hours of sleep but also the other thing, especially in the follicular phase.