A reciprocal upward and downward pedaling bicycle structure includes a main shaft of a free wheel at a chain wheel shaft, a driving body pivotally coupled to a frame of the main shaft, a pedal crank and a support rod on the driving body, and a driving belt linked to the main shaft and the support rod. An end of the driving belt is dragged to the frame by a resilient element. By the action of the resilient element ands the rotation of the main shaft, the crank and pedal are pulled by the driving belt to provide an upward bounce and the chain wheel drives the rear wheel shaft through the main driving belt. When the pedal is stepped downward, the main shaft and the chain wheel are rotated synchronously to drive the rear wheel of the bicycle to move forward.