UCC paradigm based on Web 2.0 has made new business models and came to the forefront as a commercial media. The purpose of this study is to analyze the customer attitudes toward UCC and its effects as a commercial media. Based on prior studies of Internet and Web advertising, informativeness, entertainment, irritation, trust, usefulness, ease of use, incentives, and flow were identified as affecting factors of the attitude of UCC advertising. Results show that informativeness, entertainment, irritation, trust, ease of use, and flow are significantly related to the attitude of UCC advertising, but usefulness and incentives are not. Customer attitude toward UCC advertising was also found to be significantly related to the such effects as brand attitude, word of mouth, and intention to buy. This study contributes to improve the understanding of UCC as a commercial media and provides the base of activation strategies for it.