I propose a rapid-calculation method of two-exciton states in one-dimensional tight-binding model. An equation for energy levels of two-exciton states is derived, in which energy regions including one solution are specified. Therefore, energy levels of two-exciton states can be absolutely calculated by using the bisection method. The present method dramatically improves a computation time because neither diagonalization nor summation is needed. Wave functions of the two-exciton states are also calculated immediately.