Fatigue strength of a notched plate subjected to the repeated tensile load in intermediate cycle range was analyzed theoretically by using a rule proposed by Hardrath and Ohman. On a hypothesis that a fatigue crack will initiate at a same life from a notch of any shape factor, when the accumulated hysteresis energy at the notch reaches a certain value related to material properties, the relation between the nominal net section stress range for a geometrically notched plate and crack initiation life N _c was expressed by a equation with the elastic stress concentration factor of a notch, K _t as a parameter. Also the fatigue strength reduction factor of N _c -basis, K _f , was obtained as a function of K _t and work hardening constants in the cyclic hysteresis loop. Experimental investigation was made on notched specimens, of which K _t value was varied from 1. 08 to 10. 84 in order to verify the theoretical analysis. Results of zero-to-tension axial loading fatigue test showed excellent agreement with theoretical values. The K _f , which is always lower than the K _t value, shows linear relation against K _t value. The propagation life in an unnotched and notched specimen was expressed as a function of stress range irrespectively of K _t value. The K _f value shows the increasing tendency with increasing N _c value, and the increasing amount is larger for the higher K _t value.