A verification apparatus for security documents having at least one diffractive and/or reflective security feature, includes a support device having a support surface or plane for receiving the security documents, an optical capturing device, an illuminating device for illuminating the security document, and an evaluation device which evaluates information detected by the capturing device to perform a verification of the at least one security feature. A screen is disposed between the support surface or plane and the capturing device. Light diffracted or reflected by the at least one security feature can be imaged on the screen for detection by the capturing device. The screen can be controlled with regard to at least one optical property, particularly the opacity thereof. A verification method, wherein the opacity of the screen is varied, is also provided.