A stepper includes a base, two axles, two pedal units and a coordinating unit. The axles are provided on the base so that they point downwards as they extend away from each other. Two pedal units each pivotally connected to a related one of the axles. The coordinating unit includes a lever and two connectors. The lever is pivotally connected to the base. Each of the connectors is used to connect the lever to a related one of the pedal units.