Delayed fracture properties of martensitic high strength steels have been evaluated by measuring the change in fracture stress of circumferentially notched bar specimens pre-charged with hydrogen by means of slow strain rate test (SSRT). The fracture stress of a steel with higher strength level showed sharper decrease indicating higher susceptibility to delayed fracture. It has been found that the decrease of fracture stress with hydrogen concentration follows a power law relationship when intergranular fracture mode is observed. Another finding is that the local stress and the local hydrogen concentration estimated by finite element analysis are determining delayed fracture. Hydrogen entry into steels caused by atmospheric corrosion has been evaluated as well by using cyclic corrosion test (CCT) simulating atmospheric corrosion. The circumferentially notched bar specimens were exposed to the CCT condition and SSRT was performed at humid environment to investigate both hydrogen entry and its influence on the decrease of fracture stress in the environment. The relation between fracture stress and the content of hydrogen in corrosive environment was compared with the relation of hydrogen pre-charged specimens. The SSRT combined with CCT was proposed as evaluation method considering both the effect of hydrogen in metals and hydrogen entry into metals.