Shift controlling method of a transmission

A method for controlling gear shifting of a transmission in a vehicle. The transmission is supplied with electric power from a battery or an alternator and drives an actuator to shift gear ranges of the transmission. The transmission has an output shaft that becomes difficult to rotate if a predetermined range, for instance Park range is selected when the engine stops running. The method includes determining whether a gear range differing from the predetermined range is selected when the vehicle stops traveling, and forcibly shifting the gear range to the predetermined range when a gear range differing from the predetermined range is selected by driving the actuator with electric power supplied from the alternator, and/or detecting the condition of the battery and prohibiting the stopping of the engine when, based on the condition of the battery, the battery does not supply enough electric power to drive the actuator.