To dissolve a bad influence to a human body by achieving prevention of muscular strength decline with a minimum space and minimum power in a universe gravity-free space.

A tread plate C is provided on one end of a main spring 1, a fixed plate A is provided on the other end, and shoe holders 2 are provided in the tread plate C. A middle movable plate B is fixed to the middle of the main spring 1. Guide pipes F1-F4 raised from the fixed plate A are passed through holes on four corners of the middle movable plate B, and accessory springs E1, E2 are arranged between the middle movable plate B and the fixed plate A of each guide pipe. A user puts the feet into the shoe holders 2, exerts a force with a whole body to one direction of stretching and contracting directions of the main spring 1, and performs stretching/contracting exercise. Then, a quasi-gravity is generated in the body of the user.