An exercise device providing treadmill and stationary bicycle configurations. The exercise device has a running device with a tread belt, a bicycle device with a pair of pedals, and a transmission device detachably connecting the running device and the bicycle device. Further, a controlling device for controlling the running device and the bicycle device, a sensing device for detecting exercise information of the running device and the bicycle device, a computer module comprising a program of an interactive game for the running device and the bicycle device, and a processor performing the program, and a displaying device connected to the computer module for showing the interactive game thereon according to a plurality of parameters of the program are provided.