An exercise machine includes a base, an axle rotationally supported on the base and two cranks connected to the axle. The cranks are rotational synchronously with the axle. A drive wheel unit includes an active wheel provided on the axle so that the active wheel is rotational synchronously with the cranks. A passive wheel unit includes a load wheel supported on the axle so that the load wheel is rotational relative to the axle and a passive connected to the load wheel so that the passive wheel is rotational synchronously with the load wheel. A step-up device includes a shaft rotationally supported on the base and small and large wheels connected to the shaft so that they are rotational synchronously. The small wheel is connected to the active wheel so that they are rotational together. The large wheel is connected to the passive wheel so that they are rotational together.