PURPOSE: To maintain a foot step position suitable for a user's physical condition by displacing and adjusting the position at four front and rear positions via the use of two front and rear positions of a pivoting plate on the oscillation of a parallel link, and two front and rear positions resulting from the reversal of the step at both positions of the pivoting plate.

CONSTITUTION: Each end of a pair of right and left links 7 and 8 is connected to the ends of a pair of right and left foot step support plates 1 via each pivot pin shaft 6 in such a way as capable of free turn, and the other ends of the links 7 and 8 are connected to a pair of right and left pivoting plates 9 with pivot pin shafts 10 and 11 in such a way as capable of free turn, thereby constituting a pair of right and left parallel links 12. Also, the lower sections of both foot step support plates 1 are fitted with a pair of right and left link stoppers 13 and 14. Furthermore, one link 7R is fitted with a handle projection 15 and the forward end thereof is fitted with a position selector handle 16. Also, the oscillation ends of both pivoting plates 9 are journalled to each bracket 18 of a foot step 17 with each axial bolt 19 in such a way as capable of free turn. According to this construction, the position of the foot step 17 can be displaced and adjusted at four front and rear positions.