A foldable dining chair, comprising a chair portion, a connecting shaft, a footrest lever and telescopic chair legs; the chair portion and the chair legs being connected with the connecting shaft; the chair portion being located at an upper part of the dining chair, and comprising a seat board, a backrest and a tray, and the backrest comprising a backrest frame; and four said chair legs being provided, and the chair legs being separately arranged nearby two ends of the connecting shaft and respectively frontward and rearward to form a pair of front legs and a pair of rear legs; wherein, the front legs, the rear legs, the backrest frame and the footrest lever are rotatably fitted on the connecting shaft by a front leg bushing, a rear leg bushing, a backrest frame bushing and a footrest lever bushing respectively; each of the front leg bushing, the rear leg bushing, the backrest frame bushing and the footrest lever bushing consists of a bushing body and a joint fixedly connected with the bushing body, the bushing body being a hollow annular structure, a connection mechanism being arranged on an inner wall of the bushing body, and the connection mechanism comprising several recesses and two limiting blocks; and the recesses being spacedly arranged along a circumferential direction of the inner wall of the bushing body, and the limiting blocks being arranged outside the two recesses at outermost ends; the connecting shaft is also provided with a locking device which comprises a locking block, a return spring, a moving block and a handle, the locking block being arranged on the connecting shaft in a manner of moving only along an axial direction of the connecting shaft, several bumps matching the recesses of each of the bushings being protruded on the locking block, a connecting post matching the moving block being arranged at one end of the locking block, and two ends of the return spring being respectively connected with or abutted against the locking block and the connecting shaft; the moving block being provided with a sliding slot, an orienting slot and a connecting hole, the sliding slot being respectively obliquely arranged at two ends of the moving block and matching the connecting post of the locking block, and the orienting slot being a strip-shaped sliding slot and being arranged along a movement direction of the moving block; and the handle being provided with a fixing screw hole corresponding to the connecting hole on the moving block, a fixing screw being passed through the fixing screw hole and then connected into the connecting hole, and the connecting shaft being provided with a strip-shaped hole at a position corresponding to the fixing screw hole; and the front leg bushing, the rear leg bushing, the backrest frame bushing and the footrest lever bushing are sheathed in close proximity to one another on the connecting shaft in any order; and after each of the bushings is sheathed on the connecting shaft, the limiting blocks also form several slidable slots respectively communicated with all the recesses of the same bushing at one side in a movement direction of the bumps, the size of the slidable slots matches that of the bumps, and the limiting blocks also extend into the slidable slots.