The high popularity and high demand of internet applications lead to faster development of cloud computing services that make network access become more convenient. However, using a new technology can cause users’ perceived risk because they worry about internet security and invasion of privacy. The study aims to explore the influence of end users’ perceived risk on usage intention of cloud computing services and the interactive effect of perceived risk and subjective norm on usage intention. The study dispatched 350 questionnaires to internet users. The amount of valid questionnaires is 238 and the effective response rate is 68%. The results showed that both perceived risk and subjective norm are significantly affected to usage intention, and subjective norm has a moderating effect on the relationship between perceived risk and usage intention.