Multilinear hysteresis models such as the Clough model are generally used for earthquake response analysis of reinforced concrete (RC) structures, while force-deformation relations obtained in experimental studies are curvilinear. Other hysteresis models are developed to consider features such as strength degradation at large deformation regions, stiffness degradation due to cyclic loading or inverted S-shaped slip property. However, these models are generally not widely used because most use many rules to express all the features and require many parameters, which makes the model complicated. In this study, a curvilinear hysteresis model for RC structures is developed with relatively simple rules and a small number of parameters. The model consists of only two functions, the skeleton curve and the inner loop, and nine model parameters. The developed model is applicable to various types of RC beams and columns, including strength deterioration at large deformation regions, stiffness degradation due to cyclic loading or inverted S-shaped slip property. A method to evaluate the capability of hysteresis model is developed using the minimized error index based on genetic algorithm to obtain the best parameter which will reproduce the force-displacement relations. Force-displacement relations of RC specimens are collected from previous experimental studies and the error indices are calculated. The developed model are capable of reproducing forcedisplacement relations well compared to other hysteresis models for RC structures.