A flat-proof rim for a pneumatic tire of a wheel is disclosed. The flat-proof rim includes a circular rim body having an outer periphery. A plurality of spaced linkages are arranged along and movably connected to the outer periphery of the rim body, and each have a hoof adapted to be movable between a radially inner position and a radially outer position relative to the rim body. In addition, there is provided an apparatus for driving the linkages so that the hoofs are moved from the radially inner positions to the radially outer positions when the pneumatic tire is deflated while the wheel is rotated at a high speed.