A device for judging a degree of awakening and a method for judging a degree of awakening which can more reliably detect weak sleepiness of people in action. The device for judging a degree of awakening in accordance with the present invention comprises a heartbeat sensor for acquiring a heartbeat signal from a driver and an ECU for detecting sleepiness of the driver by processing the heartbeat signal. In the ECU, a heartbeat signal preprocessing section for acquiring a heartbeat period time series from the heartbeat signal, a feature amount extracting section for acquiring a heartbeat fluctuation low frequency component power from the heartbeat period time series, a sleepiness detecting section for judging whether sleepiness occurs in the driver or not according the heartbeat fluctuation low frequency component power, a stimulus timing setting section for setting a timing for imparting a stimulus for removing sleepiness to the driver according to the heartbeat fluctuation low frequency component power, and a sleepiness removing stimulus output section for imparting the stimulus to the driver at thus set timing.
