A running data display unit (1) for a bicycle calculates running data such as running speed, running distance, average speed, maximum speed etc. of a bicycle, based on pulse signals from a revolution detecting portion (3). This calculation is performed by a microcomputer incorporated in the display unit. The running data obtained by the calculation are displayed in a digital form on a liquid crystal display panel (15). If the running data displayed on the panel (15) is the running distance, the running distance is represented as a numerical value including five figures at maximum. The running distance not attaining 1000 km (or miles) is represented down to two decimal places and when the running distance attains 1000 km (or miles), the manners of display is automatically by the microcomputer (30) changed so that display is made down to only one decimal place.