The stress-strain state and the stress concentration under the large elastic strains in the rubber specimens with the cracks or sharp notches subjected to uniaxial and biaxial tension were investigated. The cracks were placed horizontally or they were inclined. (Load direction is vertical). The investigation was carried out by means of the non-linear photoelastic method using the models made of a birefringent polyurethane resin. The nominal relative lengthening on the distance from the crack reached 55% and the maximum lengthening near the crack's tip were 120%. According to the results of the well-known theoretical solution large stresses at the cracks tip are infinite. It also concerns the large strains (V.V. Novozhilov, K.F. Chernikh). The goal of this research was to check out this statement. The experiment refutes it.