This research proposes the topology optimization method for the micro-structure of all-solid-state batteries(ASSBs) by introducing the homogenization method. ASSBs mark a remarkable advancement in battery technology, offering enhanced safety, energy density, and durability compared to conventional liquid electrolyte-based systems. Employing solid electrolytes, ASSBs effectively reduce risks like leakage and combustion, distinguishing them from liquid-based batteries. Despite substantial progress, notable challenges persist. ASSBs face ionic conductivity and electron mobility limitations due to inadequate surface contact between active materials and solid electrolyte particles in composite electrodes. Extensive research efforts have focused on material development through experimentation, although this process demands significant time and resources\cite{Koc}. To overcome these challenges, integrating systematic design methodologies such as structural optimization proves effective in achieving an enhanced internal structure, thereby improving battery performance. Therefore, we introduce the homogenization method to relate micro-structure to macroscale material properties and propose the topology optimization method for the micro-structure. The density function $\rho$ is defined within the unit cell in the microscale to represent the distribution of the active and electrolyte material. The novelties of this research are to present the objective function that can reduce the computational cost to half, to define the optimization problem, to derive the sensitivity using the adjoint method in continuity form, and to demonstrate the validity of the optimization method by illustrating the obtained optimal solution.