When we go shopping, we see that shoppers take merchandise and return it to the shelf. With focusing on this action of shopper, this research adds values to the analysis of POS-system by analyzing the action. In this paper, this action is called "confused-behavior". This paper propose a system which gets shopper's action by using RF-ID tags and explains cause of the actions. The scopes of this paper are development and evaluation of proposed system. The relation between shopper's action and usage is examined and the system is designed by considering three types of shopper's actions. The system is evaluated from the point of view of certainty to detect actual action during shopping.