This study claims the need of Cyber-Electronic Warfare(CEW) as a means of Cyber Deterrence. CEW paralysis enemy networks by using electromagnetic waves in wireless space and through cyberspace. CEW is a critical weapon system in that it enables timely attack on not only internet network but also intranet network such as nuclear-missile network. Since CEW can be used as non-lethal preemptive self-defense in case of emergency, CEW will be an absolutely indispensable means of Cyber Deterrence, especially in Korea’s security environment where South Korean society encounters flagrant cyber attacks, nuclear & missile threats and local provocations from North Korea.