CFRP laminate can be used itself as a sensor for detecting own damage. The authors have introduced electric resistance change method and asymmetrical dual charge electric potential change method to detect a delamination in the CFRP laminate. Although the methods showed good performance of estimation analytically and experimentally, those are sensitive to electromagnetic noise. Experimental error caused by such noise in the actual use may affect the accuracy of estimation. In this paper, influence of the noise on accuracy of estimation was investigated quantitatively using finite element analysis. It was clarified that the methods have different characteristics for experimental noise.