An outdoor umbrella includes an awning frame, a supporting shaft and an adjustable rotation base including a base housing and a transportation arrangement. The base housing is arranged to couple with the supporting shaft to support the awning frame in an upright manner, and includes a plurality of transferring wheels. The transportation arrangement is provided at the base housing to operate the base housing between an idle mode and a transportation mode, wherein in the idle mode, the transferring wheels are suspenedly lifted up to position above the bottom edge of the base housing such the base housing is sat on the ground surface in a stationary manner, wherein in the transportation mode, the base housing is lifted up by air pressure for allowing the transferring wheels to move out of the receiving cavity at a position below the bottom edge of the base housing.