1. A quality assurance method for radiation therapy equipment, the method comprising: (a) obtaining images for quality assurance of radiation therapy equipment by capturing at least one image of an indicating part installed on the radiation therapy equipment and indicating a mechanical-isocenter point of the radiation therapy equipment, by using an image capturing unit; (b) performing pattern matching on the captured image, by using an image center point tracking device, wherein the pattern matching comprises extracting a center point of each captured image and determining a position change of the center point; and (c) evaluating quality of the radiation therapy equipment based on movement range of the center point, by using an image analyzing device, wherein the image capturing unit captures images of the indicating part.