A three-dimensional user interface device includes a coordinate setting unit setting a three-dimensional coordinate space (3DCS) on the basis of a line-of-sight image, a virtual data generation unit generating three-dimensional area data representing a transparent virtual three-dimensional operation area (V3DOA) arranged in an arbitrary position in the 3DCS in a state in which at least a boundary of the area is visible, a display processing unit displaying a V3DOA represented by the generated three-dimensional area data by using a visible space in the 3DCS corresponding to a space shown on the line-of-sight image as a display reference, and an operation detection unit detecting an operation performed by the operator with the specific region in the V3DOA on the basis of the three-dimensional position acquired with respect to the specific region of the operator in the 3DCS and a position of the V3DOA in the 3DCS.