Photon scattering experiments on 52Cr and 138Ba were performed to resolve ambiguous parity assignments below neutron threshold energy by using completely linear-polarized photon beam generated by Laser-Compton backscattering technique. The parity of 5544 keV level in 52Cr was confirmed to be negative. The Ml transition was identified at 5098 keV in 52Cr. The 5644 keV level in 138Ba, which was tentatively assigned as Ml transition by former Compton polarimeter measurement, was clearly assigned as El transition. A parity measurement with a completely linear-polarized photon beam was demonstrated to be simple and straightforward method.