One-dimensional cubic phase silicon carbide nanowires (${eta}$-SiC NWs) were efficiently synthesized by thermal chemical vapor deposition (TCVD) with mixtures containing Si powders and nickel chloride hexahydrate $(NiCl_2{cdot}6H_2O)$ in an alumina boat with a carbon source of methane $(CH_4)$ gas. SEM images are shown that the growth temperature (T) of $1,300^{circ}C$ is not enough to synthesize the SiC NWs owing to insufficient thermal energy for melting down a Si powder and decomposing the methane gas. However, the SiC NWs could be synthesized at T>$1,300^{circ}C$ and the most efficient temperature for growth of SiC NWs is T=$1,400^{circ}C$. The synthesized SiC NWs have the diameter with an average range between 50~150 nm. Raman spectra clearly revealed that the synthesized SiC NWs are forming of a cubic phase (${eta}$-SiC). Two distinct peaks at 795 and $970 cm^{-1}$ in Raman spectra of the synthesized SiC NWs at T=$1,400^{circ}C$ represent the TO and LO mode of the bulk ${eta}$-SiC, respectively. XRD spectra are also supported to the Raman spectra resulting in the strongest (111) peaks at $2{Theta}=35.7^{circ}$, which is the (111) plane peak position of 3C-SiC. Moreover, the gas flow rate of 300 sccm for methane is the optimal condition for synthesis of a large amount of ${eta}$-SiC NW without producing the amorphous carbon structure shown at a high methane flow rate of 800 sccm. TEM images are shown two kinds of the synthesized ${eta}$-SiC NWs structures. One is shown the defect-free ${eta}$-SiC NWs with a (111) interplane distance of 0.25 nm, and the other is the stacking-faulted ${eta}$-SiC NWs. Also, TEM images exhibited that two distinct SiC NWs are uniformly covered with $SiO_2$ layer with a thickness of less 2 nm.