We theoretically study the electronic structure of interface states in twisted stacks of three-dimensional topological insulators. When the center of the surface Dirac cone is located at a midpoint of a side of the Brillouin zone boundary, we find that an array of nearly independent one-dimensional channels is formed by the interface hybridization of the surface states, even when the moiré pattern itself is isotropic. The two counterpropagating channels have opposite spin polarization, and they are robust against scattering by spin-independent impurities. The coupling between the parallel channels can be tuned by the twist angle. The unique one-dimensional states can be understood as effective Landau levels where the twist angle works as a fictitious magnetic field.