Gear-change controlling system for bicycles

To provide a bicycle shift control device that is unlikely to cause discomfort during a shifting procedure based on a simple control routine. With the shift control component 25, speed steps are raised to the next level when the bicycle accelerates or is in first gear. An upshift mode is established. In this upshift mode, the speed steps are kept unchanged until they are in third gear (which is lower than the second gear), and are switched to a lower level when they are in third gear. On the other hand, the speed steps are switched to a lower level when they reach the second gear during deceleration if the upshift mode is not established. A downshift mode is established. In this downshift mode, the speed steps are kept unchanged until they are in fourth gear (which is higher than the first gear), and are switched to a higher level when they are in fourth gear. An upshift mode or a downshift mode is established when a shift is performed, the speed is changed to a gear (fourth or third) different from the regular shift gear (first or second), and shift timing is slowed down. <IMAGE>