The present invention relates to a process for purification of novel polymorphic form of Gatifloxacin which comprises dissolving Gatifloxacin in about 15-50 volumes of methanol, removing insolubles if any, adding organic base to the solution, maintaining the solution at temperature of 30° C. to 70° C., for about 20 min to 4 hrs, followed by gradual cooling and maintaining the reaction mass to −10 to 20° C. for about 1-4 hrs, isolation and drying at temperature of about 45° C. to 65° C.