The advancement of the Internet and technology has made it possible to purchase and use different types of products and services online instead of offline. In particular, as the scale of online shopping malls is rapidly increasing, new functions have been tried and introduced to compensate for the limitation of not being able to directly wear clothes in an online mall. Among them, 3D virtual try-on is an innovative service and its technology is being advanced with continuous interest. Technological advances and interest in 3D virtual try-on have led to a variety of related studies. Most previous studies on virtual try-on have been conducted on the virtual fitting technology from the perspective of making clothes, or the effects and customer behavior from the customer perspective. However, there has been no research based on actual data of customers using 3D virtual try-on to show how virtual try-on affects sales. Therefore, this study understands the fundamental meaning of virtual -try-on as a customer experience and examines the effects of 3D virtual try-on on online sales. We create a 3D body model complemented by adding more diverse body shapes and sizes, and investigate the effects of virtual try-on on online sales through actual data. In addition, qualitative data including interviews are used to complement and interpret the results. The results show that virtual try-on affects the sales results: the average sales per customer increased by 14,000 won (13USD). The most important finding is that the return rate decreased by 27%; by filtering out incorrect sizes and fits. Virtual try-on may very well replace physical fitting rooms. This study presents an advanced technology of 3D virtual try-on and shows that virtual try-on is an effective tool to boost sales and decrease customers returns in a case study of womens casual L brand.