We are living in the digital age. Lots of people in the world are using the Internet and so we are spending our lifetime in the Cyberspace through the Internet. The Internet has a lot of good functions, for example, internet searching, internet commercial transaction, internet shopping mall, email sending, playing internet game, operating the bulletin board system etc. On the other hand, the Internet has a lot of bad functions, for example, cybercrime, like cyber hacking and virus spread, cyber contempt, cyber libel, cyber pornography, cyber gambling, cyber violence, cyber fraud etc. Today the situation of cybercrimes in cyberspace is very serious. A lot of cyberpornography has given the children so bad affect that they fell into abnormal addiction and could not live normally. And people who fell into internet gambling run through all their money. We have many laws and regulations about internet crimes. But a lot of cybercrimes are not reduced any longer. Why ? We should make a lot of efforts to reduce cybercrimes like as new lawmaking of cyber contempt, enforcement of real name using system in cyberspace, strengthening of self regulation against cybercrimes, international cooperation in field of cybercrime etc. This research has read in the Korean Association of Criminology at the Fall Seminar 2008. Contents of this article are as follows; Chap1. Introduction Chap2. Concept and Actual State of Cybercrime Chap3. Recent Situation and Causes of Cybercrime Chap4. Regulation against Cybercrime and Freedom of Expression Chap5. Some Measurements against Cybercrime Chap6. Conclusion