1. A three-dimensional display device for displaying a three-dimensional image, comprising: a gaze point obtaining unit configured to obtain a position of a gaze point of a viewer; a fusional area determination unit configured to determine a fusional area where binocular fusion is allowed, based on the obtained position of the gaze point; a correction unit configured to correct the three-dimensional image so as to suppress display of an object which is included in the three-dimensional image outside the fusional area; a display unit configured to display the corrected three-dimensional image; and a fusional area information storage unit configured to store fusional area information which indicates positions of a plurality of gaze points in a depth direction of the three-dimensional image and a plurality of fusional areas corresponding to the positions of the plurality of gaze points in the depth direction, wherein the fusional area determination unit is configured to refer to the fusional area information to determine the fusional area that corresponds to the obtained position of the gaze point.