In this research, we analyzed the social network topology of Yahoo! Kimo Auction. We took the members of Yahoo! Kimo Auction as the research target and developed a program to collect the historical records of trades between bidders and auctioneers. First of all, we randomly sampled 30 different merchandise categories for topology analysis. Then, we analyzed the auction networks and confirmed the presence of the small-world and scale-free properties, respectively. Moreover, we also found some trading behaviors of B2C model in the auction community besides the supposed C2C one. Our analytical results could help researchers to understand the social networks of auction communities and to develop other related research about online auctions.