This research presents a level set-based topology optimization method for the design of acoustic metasurface using a two-scale homogenization method. First, a homogenization method is proposed for the system of acoustic metasurfaces based on previous works so that it can be combined with the topology optimization method. Next, an optimization problem is formulated, where an objective functional is expressed by a macroscale response of the metasurface, and material distributions in the unit cell are considered as design variables. A design sensitivity is derived based on the concept of the topological derivative and adjoint variable method. We choose a waveguiding acoustic metasurface as a target of optimization, and two-dimensional numerical examples are offered to confirm the validity of the proposed method.