Abstract : This thesis describes an experimental study of the photon structure function using the CELLO detector. After a brief description of the complete CELLO detector we introduce the theoretical context and present a simulation program of the “forward detector”, which is an essential part of the CELLO detector for this analysis. This simulation program is tested and used in order to calculate an absolute normalization of the results of this measurement by small angle Bhabha scattering. The last chapter of this thesis presents the selection criteria for events with a hadronic final state. Detector effects are corrected by an unfolding procedure and the results of this measurement are shown. Finally, using the structure function formalism for events with a leptonic final state we check the validity of the hadronic measurement and the normalization. The essential physical results of this thesis are an indication for scale violation at low Q2 and the inadequacy of the standard theoretical predictions (VDM and QPM) at low Q2.