A method of controlling a transmission device in a vehicle includes determining a basic shift pattern according to whether towing is performed and road inclination during vehicle driving, determining first energy consumption according to loads of operating devices in the vehicle, determining second energy consumption according vehicle speed and the road inclination, comparing the first and second energy consumptions and a state of charge (SoC) of a battery to determine an energy compensation pattern, and determining a last shift pattern so as to correspond to the basic shift pattern and the energy compensation pattern.