An ergometer according to this invention comprises pedals rotated by an exerciser, a motor connected to the pedals, and a control device connected to the motor in order to control an operation of the motor, wherein a control mode of the control device for controlling the motor can be switched between a concentric contraction exercise mode, in which the motor is caused to function as a load while the pedals are rotated by the exerciser, and an eccentric contraction exercise mode, in which the motor rotates the pedals so that the exerciser is forced to resist the rotation of the pedals.