In this study, psychological experiments are conducted to investigate human avoidance action characteristics in a phase where harm almost reaches human eyes in a human-robot coexistence system. A situation is set up in which the sharp end-effector tip of a robot suddenly approaches the eyes of a participant sitting in front of the robot. In the analysis of the experimental results, the avoidance reaction time is defined as the time interval from when the end effector begins to approach the participant's eyes until when the participant begins to move the head for avoiding the harm due to the end-effector tip. The results suggest that the avoidance reaction time does not depend on the type of work being performed but on the initial distance between the human's eyes and the approaching object.