ASTM E 813-81 in USA and JSME S 001-1981 in Japan, Which are concerned with standard test method for fracture toughness JIC have been published. From the industrial and practical point of view, it is as a matter of course that a more economical and convenient test method is desired. In the present study, a significantly simple test method for evaluating JIC by suing a single Charpy-size specimen with a side-groove has been investigated. The materials used in the present study were SM50 A steel, HT 80 steel and SNCM 8 steel. It was found that Be2 (=B-(B-BN)2/B) is proper as the effective thickness of side-grooved specimens for calculating J-values. The maximum load point was found to coincide with the ductile crack initiation point in the 25% side-grooved Charpy-size specimen with the crack length to width ratio a/W of 0.6 From the foregoing results, a quite simple and convenient test method for estimating JIC has been proposed.