An elliptical trainer has a main frame having two opposite sides, each having a linking device, a stepping device and an interlocking device mounted thereon, wherein the interlocking device is provided to connect the linking device and the stepping device. A damping device is mounted on the main frame and operated with the two interlocking devices so as to promote exercise on the elliptical trainer. A longitudinal axis of an elliptical foot motion of each stepping device is adjusted due to a step force from an operator for changing a working stroke of the elliptical trainer.