A mountain climbing machine, which does not require connecting with an external electrical power source, includes a running belt, front and rear rollers, and a generator operatively linked to one of the front and rear rollers for generating electrical power when the running belt is running, wherein a rotational speed of said generator is controlled by a consumption of the electrical power generated from the running belt so as to provide a resistance force at one of the front and rear rollers to maintain the running belt at a constant speed without connecting to the external electrical power source.