In this study, we present a method for enhancing a function of the spatial photonic Ising machine by using time-division multiplexing. Processing of multiple signals in which spin interaction is encoded provides the representation of the Ising Hamiltonian which functions as an indicator to solve combinational optimization problems. To evaluate the performance of the proposed system, we calculated the Ising Hamiltonian by simulating light propagation. We confirmed that the optimal solution of a given Knapsack problem is effectively obtained by the proposed system.