  A novel type of resistive plate chamber, based on diamond-like carbon (DLC)
electrodes is under development for background identification in the MEG II
experiment. The DLC-RPC is required to have a radiation hardness to mass
irradiation since it is planned to be placed in a high-intensity and
low-momentum muon beam. In this study, the aging test using a high-intensity
X-ray beam was conducted to evaluate the radiation hardness of the DLC-RPC. The
accumulated charge due to X-ray irradiation reached about 54 C/cm$^2$, which is
approximately half of the one-year irradiation dose expected in the MEG II
experiment. As a result, the degradation of the gas gain was observed due to
fluorine deposition and insulators formed on the DLC electrodes. In addition,
discharges via spacers were also observed repeatedly and interrupted the
DLC-RPC operation.
