A three-dimensional display apparatus is provided that is suitable for displaying information or instruction relating to the work that the viewer is doing. The three-dimensional display apparatus has a display data generation unit for generating a plurality of display data each expressing a screen at a depth from a viewpoint of a viewer in a three-dimensional space and a lens driving unit for varying the focal length of the variable focal length lenses according to the depth of the display data generated by the display data generation unit. The display data generation unit generates the display data each expressing a different depth and causing a plurality of virtual images of the light emitting points appropriate to the depth to be perceived as being overlapped. The lens driving unit controls the focal length of the variable focal length lenses according to the depth of the display data generated by the display data generation unit in synchronization with displaying the display data on the display unit by the display driving unit.