We have studied the basic conductive characteristics in carbon nanotubes (CNTs) for the purpose of application to a high-frequency device. In the analysis, the current flow in the CNTs is viewed as the quantum transport of electronic waves. First, we analyzed the dispersion relations of electronic waves in the CNTs based on the linear combination of atomic orbitals expansion method. In addition, we investigated the current-density distributions around the circumference of the CNTs and the current-voltage characteristics by using the transfer-matrix method. As a result, the current distributions were found to be significantly controlled by both the chirality of the CNTs and the position of the current sources around the circumference. Based on these results, we propose herein a ferrite device that acts as a filter in the terahertz frequency domain. In this device, the high-frequency current flowing on the CNTs may excite and receive directly the spin waves in the ferrite film beneath them, and the operating wavelength may be controlled by means of the chirality via the current-density distributions on the CNTs. In addition, we found that the performance of the device can be improved by using the p-type CNTs as the excitation electrodes rather than the intrinsic CNTs.