According to an embodiment, a medical image processing device includes a first image acquirer, a second image acquirer, a direction acquirer, and a movement amount calculator. The first image acquirer acquires a three-dimensional first image obtained by photographing the inside of a body of a patient. The second image acquirer acquires a three-dimensional second image of the inside of the body of the patient imaged at a timing different from that of the first image. The direction acquirer acquires information about an irradiation direction of radiation to the patient in a treatment room. The movement amount calculator outputs a movement amount signal indicating the amount of movement of the second image to be moved to align the position of the patient shown in the second image with the position of the patient shown in the first image based on the path of the radiation set in the first image and the information about the irradiation direction.