Abstract: A breast support device for radiation therapy includes a cuplike body with a through aperture. The cuplike body has a base portion and a compression portion connected continuously forming a concave inner surface, the compression portion is extended from the base portion, the concave inner surface have contours that fit over the female patient's breast as patient been in a predetermined posture. The through aperture is formed on the cuplike body to receive a portion of the female patient's breast through, it has a contour curve defined by a cutting plane and the contours of the patient's breast.