A method or apparatus for examining a security element of a value document involves at least one optical property of the security element influenceable by a magnetic field. The value document is transported through a magnetic field which is inhomogeneous transversely to the transport direction and/or is changed time-dependently. An image of at least one portion of the value document having the security element is captured and image data describing the image are formed. The optical properties of the security element are influenced by the magnetic field, and the image data is checked whether they have a location dependence transverse to the transport direction corresponding to the location dependence of the magnetic field and/or have a location dependence in the transport direction corresponding to the time dependence of the magnetic field.