[en] We have developed a MTCA.4-based LLRF system for the injector LINAC of the next generation synchrotron radiation facility. This LLRF system consists of RF frontends, digital-analog conversion parts with ADC and DAC, and on-board processing circuits. By using this system, we can set, monitor and apply feedback-control to the phase and amplitude of the RF signals for acceleration cavities within a single module. The MTCA.4 modules have high performance and high channel density features, and thus we can build compact and high-speed systems with small amount of cables and reasonable costs. It also provides better usability on operation such as controlling and configuring operational parameters remotely via networks. We describe the architecture of the MTCA.4-based digital LLRF system, and the results of the performance evaluation tests, such as resolutions and stabilities, obtained with prototype modules. (author)