A shifting control method for controlling a speed change of a vehicle in a downhill section may include collecting, by a forward road grade information collection device, information on a downhill grade which is present ahead of a vehicle, before a vehicle enters a downhill section, determining, by a driving information detection device, whether a predetermined inertial driving condition is satisfied, before the vehicle enters the downhill section, and deciding, by a control device, a shifting mode of the vehicle depending on the downhill grade, and controlling a transmission according to the decided shifting mode, at a predetermined time before the vehicle enters the downhill section.