An improved pedal driving device of a standing type bicycle includes driving sprockets installed at positions of first and second rotating shafts of first and second cranks respectively, and a chain installed between the two driving sprockets for rotating the two driving sprockets synchronously, such that left and right pedals pivotally and respectively installed between other ends of the first and second cranks and provided for pedaling by a user's legs, and when the first and second cranks drive the first and second rotating shafts to rotate, the two driving sprockets and the chain are operated together to rotate the first and second rotating shafts and the first and second cranks synchronously and drive the left and right pedals to revolve along an elliptical track with a clash-free and smooth movement, so as to achieve a smooth, comfortable and safe operation of the bicycle.