A joint support adjustable device is provided, including a base, two connecting members and a positioning mechanism. The base has a center and two side walls distanced from and corresponding to each other, and at least one said side wall is formed with a plurality of toothed recesses. Each said connecting member is for being connected with a human limb. The positioning mechanism has a fixation member disposed between the two side walls and at least one adjusting mechanism connected with the base, each said adjusting mechanism has a positioning assembly for being operated from outside and movable about the center, at least one of the positioning assembly and the fixation member is magnetic to attract the other so that the positioning assembly has a tendency to move toward the center.
