In this report, the effects of cycle frequency, mean stress, temperature of corrosive and cathodic protection on the fatigue crack growth of mild steel are examined by using the center-notched specimens under more extensive test conditions of corrosion fatigue than those in the previous report. The results obtained are summarized as follows ; (1) The correlation between the range of stress intensity factor Δ K and the crack growth rate da/dN for mild steel in 3% salt water could be given by the power's law shown in the following equation da/dN = C (Δ K ) ^3.5 irrespective of the test conditions of corrosion fatigue such as cycle frequency f , mean stress and temperature of corrosive. (2) The coefficient C in above equation could be given by the following equation C =- A log f + B , where the coefficients A and B are material constants depending on the intensity and temperature of corrosive. (3) The crack growth rate under pulsating tension in salt water is unaffected by mean stress, and dependent on stress amplitude and cycle frequency. (4) The cathodic protection is scarcely valid for retarding the crack growth in salt water.