The purpose of this study is to suggest the situation of parking lots that increases customers' probability to visit unscheduled destinations. In this study, customers are assumed to be personal car users. A questionnaire survey was carried out to investigate the characteristics of customers' shop-around behavior in the center of Sapporo, for example, the customers' predetermined destinations, the threshold walking distance between a predetermined destination and a parking lot used, and so on. A model using random utility function is developed to estimate customers' probability to visit any unscheduled destinations. According to the model, it is clarified that customers tend to visit unscheduled destinations as the distance between a predetermined destination and a parking lot becomes longer. Also, the threshold walking distance is estimated by using the random utility function. This model gives a result that the customers tend to use a parking lot situated near predetermined destination. Considering the results given by both models, it is clarified that when the distance between a parking lot and a predetermined destination is about 430 meters, customers' probability to visit unscheduled destinations is efficiently increased when no services with respect to parking fee is provided.