A housing is adapted to be placed on a floor and is provided on its top face with a left foot support 2a and a right foot supports 2b respectively bearing left and right feet of a user. A drive unit 3 is provided to displace the left and right foot supports 2a and 2b in a mutually linked manner. The drive unit 3 is configured to reciprocate the left and right foot supports 2a and 2b in a forward/rearward direction respectively along individual travel paths La, Lb, while varying a lateral distance between said left and right foot supports with regard to representative points of the left and right foot supports. The lateral distance between forward ends of the travel paths is made greater than the lateral distance between rearward ends of the travel paths.