Emotional state before sleep affects the subsequent sleep onset. The purpose of this study was to investigate how positive/negative emotion before sleep effected hypnagogic state. The movies eliciting positive or negative emotion were presented before sleep. Hypnagogic imagery was recorded as a probe of emotional experience and EEG microstate analysis was used for finding the emotion related EEG activities. The score of emotion ratings for hypnagogic imagery indicated that positive emotion was reported in not only positive condition but also in negative condition. This implied that hypnagogic state might be accompanied by positive emotion. Comparing the appearance of maps obtained from microstate analysis between conditions, the map of right temporal activity was significantly greater in positive condition while the map of the left frontal activity was greater negative condition. These results suggested that the emotion not just in presleep but also in hypnagogic state was involved in sleep onset process.