GOC Cosmetics Store is a shop that sells various cosmetic brands that are currently busy with customers. So many transactions are made every day resulting in a lot of data transactions. The GOC store has several problems, such as the complexity of knowing which products are often sold, so that the GOC Cosmetics store cannot find out which cosmetics are out of stock. So that the writer of transaction data can be processed using data mining to process data knowledge on a large scale efficiently and effectively. And using a priori algorithm as a method that connects the interrelationships between elements. To find out what item set relationships occur in the transaction process, using the a priori algorithm is the first algorithm used when doing the association process. The results of this study indicate that if you buy SS you want to buy KN with a support value of 69% and a confidence value of 88% so that this data can provide advice to the store to improve products and further improve product sales strategies to achieve a large profit value.Keywords: