The authors have proposed the formation of dumbbell-shape graphene nanoribbon (DS-GNR) by changing the width of the mid-part of a GNR in order to enhance the stability and reliability of the GNR-based electronic devices. In this study, the electronic band structure of the DS-GNR was analyzed by using the first principle calculation method. Throughout the calculation, the electronic band structures, densities of states, and orbital distributions were examined to describe the electronic properties of DS-GNRs. The band gap of DS-GNRs is different to that of single GNRs because the orbital distributions of the lowest unoccupied molecular orbitals (LUMO) and the highest occupied molecular orbitals (HOMO) in DS-GNRs changed from those in single GNRs. Generally, single GNRs exhibit both the semiconducting and the metallic properties depending on the ribbon width. The magnitude of the band gap of DS-GNRs depends on the difference in the width of narrow part and wide parts, and the variation of the band gap of DS-GNRs was smaller than that of single GNRs. In addition, when a dumbbell-shape GNR undergoes a uniaxial tensile strain, its band gap showed high strain sensitivity as was expected. Therefore, the GNR material with a dumbbell-shape structure has great potential for use in highly sensitive strain sensors.