On the large structures such as ships's hull, tank structure and etc., various loads are acting. In some structural members, therefore, out-of-plane stress due to bending often may become larger than in-plane stress due to stretching. In this report, the characteristics of brittle fracture initiation of mild steel plate with a through crack under the combined action of stretching and plate bending have been studied both experimentally and theoretically using the linear elastic fracture mechanics (L. E. F. M.). As the results of this investigation, the following conclusions are obtained. (1) Effect of bending load on the characteristics of brittle fracture initiation can be evaluated over a fairly wide range by the criterion proposed by authors using the concept of energy balance based on L. E. F. M. (2) From the results of eccentrically loaded and center-notched Deep Notch Tests, it is extremely safe for design that the maximum surface stress is considered as the equivalent fracture stress at higher temperature than -180°C. (3) The evaluation of fracture phenomena using the equivalent K -value proposed by authors is confirmed to be fairly good for expressing the behaviour of the material such as mild steel plate.