An analytical model for a cracked reinforced concrete (RC) element is proposed on the basis of in-plane shear tests of RC panels. The proposed model can deal with both compressive failure of concrete strut and sliding failure along crack surfaces. Through comparisons of the analytical results of RC panels subjected to in-plane shear with the test results, good agreement was obtained on the nonlinear behavior including the ultimate strength. Furthermore, based on comparisons with other analytical models on the strength reduction of cracked concrete and the shear transfer stiffness of crack surfaces, the advantage of the proposed model was confirmed.