We studied the optical and structural properties of conventional and ion-beam-assisted-deposition (IBAD) Nb$_2$O$_{5}$ films which were evaporated by an electron beam gun. The vacuum-to-air spectral shift and the cross sectional SEM images of the Nb$_2$O$_{5}$ films were investigated. The results show that the IBAD Nb$_2$O$_{5}$ films have a higher packing density than the conventional Nb$_2$O$_{5}$ films. The average refractive index of IBAD Nb$_2$O$_{5}$ films was increased, while the extinction coefficient was decreased compared with the conventional films. As the oxygen flow was increased, the average refractive index and extinction coefficient of the conventional and IBAD films decreased. Both the conventional and IBAD Nb$_2$O$_{5}$ films showed inhomogeneity in refractive index, and the degree of inhomogeneity of the IBAD Nb$_2$O$_{5}$ films became larger as the ion current density was increased. All Nb$_2$O$_{5}$ films were found to be amorphous by x-ray diffraction (XRD) analysis, and hence the crystal structure of Nb$_2$O$_{5}$ films was not changed by IBAD.