Hull structural steel plates suffer from some embrittlement when they are subjected to bending by the line heating process. The embrittlement, however, is localized in some limited zone of the plate thickness. Therefore, the full thickness behavior should be examined in one way or another, in order to predict the service performance of the plate. The authors propose a simple method of notch toughness evaluation for this purpose by means of the van der Veen test with a sufficiently deep notch. The transition temperature determined by the proposed testing is deemed as a parameter indicating the full thickness characteristics with respect to propagation arrest of brittle fracture. It is clarified that the increase in the said transition temperature is 10°C or less for the line-heated plate steel as the whole thickness, although the V-Charpy transition temperature increases by a large amount of 55°C if the specimen is taken from 2 mm below the line-heated surface. Tested materials are 50 kg/mm² class hull structural plate steels ; conditions of the line heating process are desirable ones in view of the practical efficiencies.