The distribution of fatigue crack growth rate is influenced by the measuring interval and methods of calculation of crack growth rate. The purpose of this paper is to suggest a method for the evaluation of crack growth rate distribution without the influence. The constant ${Delta}P$ test and the constant .DELTA.K test are executed by using the CT specimen. The measuring interval of (${Delta}a$/W=0.0067~0.014) crack length is not affected by methods of the calculation of the fatigue crack growth rate is suggested.