Website is an entity which is not separated in e-commerce industry, quality and reliability of website needs to be concerned by stakeholders in e-commerce industry. WebQual 4.0 is a method of quality measurement of website through user perceptions based on three dimenssions includes usability, information quality, and service interaction quality. The population of this research are the active users whoc access website e-commerce XYZ amounted 100 repondents which are selected using purposive sampling. The research method used in this research is survey with WebQual 4.0 based questionnaire which is analyzed using IPA (Importance Performance Analysis) to find out the level of usr satisfaction which is comparison or GAP between interest and performance. The results of the validity and reliability test showed that the whole questionnaire items were valid and reliable because they had fulfilled the requirements and were understood by the respondents. The results showed that of the 22 items analyzed by the IPA method were grouped into quadrant I (6 items), quadrant II (4 items), quadrant III (5 items) and quadrant IV (7 items). The items that are considered important and need to be improved are located in quadrant I, which are the provision of accurate, detailed information, appropriate format, security when making transactions, ease of communication with parties of e-commerce XYZ, and compatibility of products to be delivered.