Provided is a phantom device having an internal organ simulating phantom. The phantom device comprises: a phantom receiving radiation emitted from a radiation emitting unit and comprising therein a simulant that simulates an internal organ; a lifting unit installed under the phantom to support the phantom and moving the phantom relative to the radiation emitting unit, the lifting unit comprising: a worm shaft axially rotated by an external torque and having a worm formed on an outer circumferential surface thereof, a cylindrical worm wheel having gear grooves formed on an outer circumferential surface thereof to engage with the worm and a female screw formed on an inner circumferential surface thereof, and rotated by the axial rotation of the worm shaft; and a driven screw engaging with the female screw of the worm wheel, and moved up and down by the rotation of the worm wheel to move up and down the phantom; and a horizontal moving unit interlocking with the lifting unit and horizontally moving the phantom. Accordingly, since the phantom device can simulate any movement pattern, even the respiratory movement pattern of a patient's internal organ to accurately determine a desired dose of radiation to be delivered to the body part, high quality assurance of radiation therapy equipment can be achieved and therapeutic effect can be improved.