The purpose of this study was to investigate the relationship between arousal level and blink activity; blink rate, blink amplitude and blink duration. Blink activity was examined under two different tasks in which arousal level was manipulated. One was a vigilance task (Experiment 1) for comparatively high arousal level. The other was a simple counting task in a dark and quiet room (Experiment 2) for extremely lower arousal level. Results indicated that blink rates and blink durations tended to increase as arousal level got lower in the monotonous vigilance task situations, meanwhile, blink rates and blink amplitudes decreased as a function of negative arousal level in the pre-sleep situation.