Purpose: The purpose of this study was to explore the relationship between cyber leisure activity and autonomic function in high school students. Methods: The subjects of this study were 242 second graders at high school located in D city. The research design was descriptive correlation study. Data were collected from August 26 to September 17, 2010, using a cyber leisure questionnaire and heart rate variability (SA-6000, Medicore, Korea) for autonomic function. Results: Total time for the cyber leisure activity was 391.3± 262.0 (min/week). Time for internet usage and computer game was 234.5±140.1 (min/week) and 156.8±164.3 (min/week), respectively. There were significant positive correlation between total cyber leisure time and sympathetic activity (r=.247, p<.001). Conclusion: Excessive cyber leisure activity could increase sympathetic activities in high school students. Thus, nursing intervention to reduce the total cyber leisure time will be helpful to improve their neurophysiological status.