In this paper, we propose "Paper Windows", a paper interface that can use on the capacitive touch-panel display. Operating through a window on the card allows the user to use it as an independent touch-panel display. Using a paper card can give a user feeling like "using a small touch-panel display". And we also propose a creating method for interface using inkjet printer with conductive ink. This allows a user to create an interface easily and at a low cost. Furthermore, we experimented on the recognition accuracy of the interface that are painted conductive points.