We study the boundary regularity of solutions of the Dirichlet problem for the nonlocal operator with a kernel of variable orders. Since the order of differentiability of the kernel is not represented by a single number, we consider the generalized Hölder space. We prove that there exists a unique viscosity solution of Lu = f in D, u = 0 in R n \ D, where D is a bounded C 1,1 open set, and that the solution u satisfies u ∈ C V (D) and u/V (d D ) ∈ C α (D) with the uniform estimates, where V is the renewal function and d D (x) = dist(x, ∂D).