Autonomous docking is an essential capability to complete maritime missions for unmanned surface vehicles (USVs). This study presents a control procedure of autonomous docking for a USV based on reachability analysis which is a formal method to guarantee the feasibility of reaching goal states safely and design a sequence of optimal control inputs with constraints while overcoming disturbances. The USV's kinematic model is considered and a set of control inputs that guarantees successful docking in disturbances while satisfying the constraints is determined using reachability analysis. For this, the target pose and the dock are defined as level sets of signed distance functions, and the Hamilton-Jacobi partial differential equation with constraints is solved numerically.