An input device is to input a shape of a measurement target is response to a signal transmitted from a stylus pen, to determine positional relation between a position of a marker and a shape of the measurement target. The marker is attached to the measurement target and detectable by a cerebral-function measuring device. The input device includes a controller, and a display unit. The controller is configured to generate a screen in which a three dimensional shape of the measurement target and a guide of a position to be acquired next with the stylus pen are superimposed. The display unit is configured to display the screen generated by the controller, on a display portion.
