Since carbon nanotubes (CNTs) have unique electronic and mechanical properties, there have been many efforts to develop CNTs-based electronic devices and sensors. The authors have also validated the possibility of a highly sensitive strain sensor using popular resin in which multi-walled CNTs (MWNTs) were dispersed uniformly. It is, however, indispensable for clarifying how to change the electronic state of a deformed CNT for assuring the stable performance of the sensor because the reported sensitivity has ranged widely. In this study, the relationship between the deformation characteristic of a CNT under strain and its electronic properties was analyzed. The analysis result obtained from density functional theory (DFT) calculation showed that the orbital hybridization was occurred when the maximum local dihedral angle exceeded 10-20 and 25-30 in GNRs and CNTs, respectively, which induced the band gap.