1. An image correcting method, comprising: attaching a marker to an object, and generating a first non-real-time image, of a first image type, and a first real-time image, of a second image type, including the object's anatomical information about a surrounding region including a position of the marker when the object is in a first pose; generating a second real-time image, of the second image type, of the object about the surrounding region when the object is in a second pose; obtaining shift information of the marker based on the first real-time image and the second real-time image when the object is changed from the first pose to the second pose; correcting, in a processor, the first non-real-time image based on the shift information of the marker; and displaying the corrected first non-real-time image on a monitor; wherein the obtaining of the shift information of the marker comprises: determining a point at which a value measured in data included in the first real-time image exceeds a threshold value, and specifying a first pose relationship between the point and the marker; selecting a point, corresponding to the point determined in the first real-time image, on the second real-time image, and specifying a second pose relationship between the point selected on the second real-time image and the marker; and calculating a shift direction and a shift amount of the marker when the object is changed from the first pose to the second pose using the first pose relationship and the second pose relationship.