Abstract: A hinge device of a foldable chair. The foldable chair includes a front tube, a middle tube, a rear tube and a foot stand. Three-way hinges each including a first pivoting portion, a second pivoting portion and a third pivoting portion connect the front tube, the middle tube, the rear tube and the foot stands together. The characteristic lies in that the third pivoting portion is shifted from a straight line connecting the first pivoting portion to the second pivoting portion so that the third pivoting portion and the first and second pivoting portions are disposed alternately and all the pivoting portions after being folded form a right-angle arranged pattern. The foot stand is folded on the inner side of the middle tube and arranged in parallel to inner and outer portions of the middle tube.