In rapid prototyping technologies (RP), especially in Polymer Jetting (PJ) or Streolitography (SLA), several types of polymers are used, which in the process of building models are cured by ultraviolet light (UV). Knowledge of the mechanical properties of these photopolymers is an important issue in engineering practice (design stage) and in the operation of various elements (models) manufactured of these materials. In this study, we applied the PolyJet technology to use two types of photopolymers: commercially available VeroWhite, characterized by high stiffness, and commercially available TangoGrey, possessing high elasticity. The static and the dynamic tests are used to identify viscoelastic properties of the photopolymers. Tests relaxation, according to ISO 3384: 2002, were performed on samples of cylindrical shape using the testing machine Inspect Mini. The experimental results were approximated using a five-parameter rheological model, ie. comprising two Maxwell models coupled in parallel with a Hooke’s model. Fitting the relaxation function to the particular results obtained in the experiment was performed by means of the Origin program. A non-linear regression method based on the Levenberg–Marquardt algorithm was used.