In this paper, we show the maximal regularity of nonlinear second-order hyperbolic boundary differential equations. We aim to show if the given second-order partial differential operator satisfies the specific ellipticity condition; additionally, if solutions of the function, which are related to the first-order time derivative, possess no poles nor algebraic branch points, then the maximal regularity of nonlinear second-order hyperbolic boundary differential equations exists. This study explores the use of taking the positive definite second-order operator as the generator of an analytic semi-group. We impose specific boundary conditions to make this positive definite second-order operator self-adjoint. As a linear operator, the self-adjoint operator satisfies the linearity property. This, in turn, facilitates the application of semi-group theory and linear operator theory.