This paper describes the applicability of passive electric potential CT (computed tomography) method which does not require electric current application for damage detection. In this method, piezoelectric film is glued on the surface of structures as a sensor. Electric potential values on the piezoelectric film change due to the strain distribution on the structure, when the structure is subjected to external load. The strain distribution of the cracked body induces a characteristic electric potential distribution on the piezoelectric film. Therefore passively observed electric potential values on piezoelectric film can be used for the defect identification. An inverse method based on the least residual method was applied to the crack identification from the electric potential distribution. In this inverse method, square sum of residuals is evaluated between the measured electric potential distributions and those computed by using the finite element method. This method may be applied to develop an intelligent structure with a function of self-monitoring of flaws and defects. The electric potential on piezoelectric film was measured by the contact type and the non-contact type methods. The measured electric potential distribution was used to identify a crack by using the present inverse method. It was found that the location, size and depth of the crack can be quantitatively identified by the passive electric potential CT method.