The present invention relates to a method and a device for calibrating an irradiation device of an apparatus for generatively manufacturing a three-dimensional object. The calibration includes steps of arranging an image converter plate (12) in or in parallel to a working plane of the apparatus, wherein the image converter plate (12) outputs detectable light (13), when the irradiation device irradiates predetermined positions of the image converter plate (12) with energetic radiation; of scanning the image converter plate (12) by the irradiation device; of detecting the detectable light (13) by a light detector (15); of determining coordinates of the irradiation device, when the detected light (13) is detected; of comparing the determined coordinates with predetermined reference coordinates; and of calibrating the irradiation device on the basis of a deviation between the determined coordinates and the reference coordinates.