Abstract: A pneumatic ab wheel includes shaft having a middle section and two holding sections, a rotation assembly pivotally connected to the middle section of the shaft and performing a rotational movement on the shaft, and a wheel provided around the rotation assembly to drive the rotation assembly to perform the rotational movement on the shaft and to roll on a surface while in contact with the surface so as to generate a frictional force. The wheel is filled therein with at least one gas to form a pneumatic pressure in the wheel. When the pneumatic pressure in the wheel is adjusted, the frictional force between the wheel and the surface is changed.