Provided is a technique with which it is possible to measure a subject's reaction by moving a visual target object in an arbitrarily defined direction as well as a horizontal direction. A dynamic visual acuity measuring device includes a projector projecting an index image pattern, a reflecting mirror reflecting light from the projector, a screen receiving light from the reflecting mirror and displaying the index image pattern, a movable casing holding and maintaining relative positions of the projector, the reflecting mirror, and the screen, a fixed casing supporting the movable casing, and a rotating shaft linking the movable casing rotatably to the fixed casing. In this device, the index image pattern displayed on the screen is moved in one direction by the reflecting mirror being displaced and a direction of movement of the index image pattern is changed in a coordinate system fixed to the fixed casing by the rotating shaft being rotated.
