A stepper includes a base, two axle units, two pedals and a coordinating unit. The base includes a post formed thereon. Each of the axle units includes an axle extended downwards from the post. Each of the pedals includes a pedal pivotally connected to the axle of a related one of the axle units. The coordinating unit includes a lever pivotally connected to the post and formed with two ends each in contact with a related one of the pedals so that one of the pedals is moved upwards and outwards while the other pedal is moved downwards and inwards.