In this paper we study boundary controllability of the Korteweg-de Vries equation posed on a finite domain with the Neumann boundary conditions. We consider the cases where one, two, or all three of those boundary data are employed as boundary control inputs. To get the main result, the system is first linearized and the corresponding linear system is proved to be exactly boundary controllable if using one, two, or three boundary control inputs. In the case where only one control input is allowed to be used, the linearized system is shown to be exactly controllable if and only if the length of the spatial domain does not belong to a set of critical values. Then the nonlinear system is shown to be locally exactly controllable around a constant steady state if the associated linear system is exactly controllable.