A shifting control system has two gear shift stage groups, two clutches, a clutch release detection section, a pre-shift controller, a clutch oil level detection section and a pre-shift inhibiting section. The clutches are alternately engaged to selectively transmit power from an engine to a wheel. The clutch release detection section detects a release-side clutch which corresponds to the clutch that is in a released state. The pre-shift controller operates a meshing mechanism of the gear shift stage group corresponding to the release-side clutch, so as to undergo pre-shifting when the other clutch is engaged as an engage-side clutch. The clutch oil level detection section determines whether an oil level in the release-side clutch is equal to or greater than a preset oil level. The pre-shift inhibiting section inhibits pre-shifting while the oil level in the release-side clutch is equal to or greater than a preset oil level.