A micro-adjustable supporting device includes a mounting seat, a movable unit, and an adjusting unit. The movable unit includes a rotating assembly disposed rotatably in the mounting seat and rotatable about an axis, and a bottom seat assembly disposed under the mounting seat and rotatable about the axis. The adjusting unit includes a pair of spaced-apart first and second tilt-adjusting elements, and an angle-adjusting element. Each of the first and second tilt-adjusting elements extends through the rotating assembly to connect with the bottom seat assembly, and is movable relative to the rotating assembly in a direction parallel to the axis to adjust a tilt angle of the bottom seat assembly relative to the axis. The angle-adjusting element is operable to move relative to the mounting seat to thereby rotate the rotating assembly and the bottom seat assembly about the axis.