To provide visually-impaired people access to graphical information, we previously developed a device called a “tactile mouse.” It consists of a computer mouse and a small tactile display. Tactile information is fed back to the fingers according to the mouse's movements, giving the user the feeling of exploring tangible drawings. Because the tactile display is small, however, users tend to deviate from the tangible graphics when they move the mouse too much. To identify conditions for reducing this deviation, we conducted two experiments : one on line following and one on shape discrimination. We found that when the parameter called “hand-movement-to-pin ratio” was too low, the chances of deviation increased, and when it was too high, discrimination failures occurred more frequently. Consequently, intermediate conditions that led to less deviation and fewer discrimination failures were found to be adequate for the efficient use of the tactile mouse.