Shear failure of reinforced concrete beams is still a point of research. The use of dolomite (good quality crushed limestone) or basalt besides the gravel (common used in Egypt) as a coarse aggregates for reinforced concrete structures has been common in Egypt recently. The effect of these different types of coarse aggregate and its size on shear behavior of reinforced concrete beams had been studied experimentally using 18 specimens of reinforced concrete beams. The shear span to depth ratio (a/d) had been used as a main variable through this research. All beams had the same longitudinal and web reinforcement. The difference in concrete compressive strength between the different concrete mixes was insignificant. For the prediction of the shear strength values of the tested beams, three formulae are used. The first one is an empirical formula based on statistical analysis. The other two formulae are based on Size-Effect Law. The experimental shear strength of the tested beams was determined and compared with the calculated values from the previous formulae. The study showed good results of concrete shear strength for different types of coarse aggregate specially the dolomite. For dolomite and basalt, the concrete shear strength increased as the coarse aggregate size increased. The calculated values of concrete shear strength from the different applied formulae showed acceptable agreement with the experimental values. The formulae based on Size-Effect Law achieved smaller deviations of the measured values from the predicted ones. The effect of aggregate size was given only by the basic formula based on Size-Effect Law.