  We propose a scheme for generating the Schr\"{o}dinger cat state based on
geometric operations by a nanomechanical resonator coupled to a superconducting
charge qubit. The charge qubit, driven by two strong classical fields,
interacts with a high-frequency phonon mode of the nanomechanical resonator.
During the operation, the charge qubit undergoes no real transitions, while the
phonon mode of the nanomechanical resonator is displaced along different paths
in the phase space, dependent on the states of the charge qubit, which yields
the Schr\"{o}dinger cat state. The robustness of the scheme is justified by
considering noise from environment, and the feasibility of the scheme is
discussed.
