The aim of this thesis is to design and test a device for biaxial tensile loading of rubber-like materials. Basic equations needed to describe the material response are provided. Based on the investigation of existing solutions, a mechanism for use on uniaxial tensile testing machines has been developed. Finite element analysis was used to determine a suitable shape of a test sample for the biaxial tensile test. Uniaxial and biaxial tensile experiments were performed on a rubber-like material. From these results Mooney-Rivlin and Ogden model parameters are determined for both hyperelastic materials responses and both types of experiments.