The optical properties of the transparent wavelength-conversion film containing 38.8 wt % YVO4:Bi3+,Eu3+ nanoparticles of 10.8 +/- 1.6 nm in size are compared to that of the film containing 30.0 wt % micron-sized particles of 1.12 +/- 0.48 mu m in size. The photoluminescence intensity at 619 nm corresponding to the f-f transition of Eu3+ for the film containing nanoparticles increases with increasing the film thickness up to 400 mu m, whereas that of the film containing micron-sized particles reaches the maximum at the film thickness of similar to 40 mu m. The transmittance at 619 nm for the former is similar to 96% irrespective of the film thickness, whereas that is less than 0.17% for the latter. These results suggest that the transparent film of YVO4:Bi3+,Eu3+ nanoparticles has markedly low light-scattering loss.