Purpose: This study aimed to analyze the degree to which information from Social Networking Systems (SNS) affects purchase behavior and investigates how customer involvement influences their choice of SNS information sources and purchase behavior. Methods: SNS information sources were categorized into three types: corporate-led, customer-led, and neutral type. Purchase behavior was divided into three stages, namely pre-purchase, during purchase, and post-purchase stages. High and low degrees were used to quantify customer involvement. Adults between 20 and 50y who frequented restaurants and had experience in using SNS participated in a self-administered survey. (response rate: 95.1%). Repeated measures ANOVA and logistic regression were used for data analysis. Results: Customers used each information source to a significantly different degree at each stage of purchase(p<0.05). The high involvement customer group was affected by all three types of SNS information sources 2.153~6.315 times more than the low involvement customer group. This result shows that customers utilize subjective and objective information to make smart decisions through diverse information sources. The degree of interest in eating out seems to affect the utilization of SNS information sources. Conclusion: A restaurant should identify the customers’ favorite channel to get restaurant information and understand new customer behavior in information searching and distribution attitudes that affect word-of-mouth(WOM) marketing. This understanding of customer behavior will help the restaurant industry keep a continuous relationship with customers and communicate closely with them in strategic online marketing.