A user interface device includes: a display unit which displays a two-dimensional or a three-dimensional display object in a display space; a sensor unit which measures 3D coordinates of fingers of a user in the display space; a motion detecting unit which detects motion of the fingers of the user relative to the display object based on the 3D coordinates of the fingers of the user measured by the sensor unit; and a display control unit which changes display content displayed by the display unit, according to a detection result obtained by the motion detecting unit.