Today, with so many developed new communication technology, it is indispensible to modern people absorbing and searching information through the Internet. By both receiving and releasing news, it is getting more easier to us sharing ideas, exchanging information, having more interactions and maintaining closer relationship nowadays. Based on such situation, the relationship and trust among people would sometimes cause massive influence than mass communication media. luence we have is more than mass media. The service of ¡§Facebook Places¡¨ has been creating a massive trend to millions of users to leave a message or upload a photo by ¡§check-in¡¨ via Facebook recently no matter where, when, what or with who. And such situation has plenty of similarities with the ¡§Word of Mouth¡¨ concept which we have learned before. Based on the Word of Mouth theory, the aim of the research is to discuss if the effect of ¡§Word of Mouth¡¨ and the consumer behavior would be influenced by Facebook ¡¨check-in¡¨ service. The research is focusing on 300 Facebook users ( no matter one who have tried the ¡§check-in¡¨ service before or not) through questionnaires by paper and online. In conclude, it is related between the effect of ¡§Word of Mouth¡¨ and Facebook ¡§check-in¡¨ service, because most users would have much concerns on these places or stores appearing on Facebook via ¡§check-in¡¨ service, and would have high willingness to visit them since their friends or families have ¡§check-in¡¨ before.