A great number of loading tests have been performed on load-carrying behaviour of RC members with the corroded reinforcing steel. However, it is difficult to find the quantitative relationship between the degree of corrosion and the loading capacity. This may be attributed to a scatter in the results of the loading test due to the non-uniformity in the reduced cross sectional area of the corroded reinforcement and some differences in the experimental technique. Such scatter of the results also leads to the difficulty in the selection of the target of the numerical analysis, which must be useful for the estimation of the structural performance. JSCE (Japan Society of Civil Engineers) Committee 331 conducted a systematic laboratory test on the structural performance of RC beam deteriorated by the corrosion of the reinforcement according to the common experimental procedure. The objectives of the common test are to grasp the essence of the scatter in the result of load-carrying capacity. In this study, the flexural behaviour of RC beam, which is degraded due to the chloride ion attack, was focused on without taking into consideration shear failure or bond failure of the tensile reinforcement. The results of the common test show that the large ratio of the corrosion weight loss was highly likely to induce the failure due to the fracture of the longitudinal reinforcement, because the longitudinal scatter in the cross-sectional area of corroded reinforcement increases as the corrosion loss increases.