A wheelchair characterized by: a chair frame mechanism including a frame body, and two pedal-mounting rods that are disposed at a front side of said frame body; and two pedal mechanisms respectively mounted to said pedal-mounting rods, each of said pedal mechanisms being able to be positioned relative to said corresponding pedal-mounting rod at a close position and an open position, each of said pedal mechanisms including a pivot unit that is sleeved on said corresponding pedal-mounting rod and that is rotatable about and movable along said corresponding pedal-mounting rod, a positioning unit that is mounted to said corresponding pedal-mounting rod, that partially projects out of an outer surface of said corresponding pedal-mounting rod, and that engages said pivot unit, and a pedal unit that is mounted to said pivot unit, said pivot unit of each of said pedal mechanisms having a guide groove that is formed in an inner surrounding surface thereof and that is slidably engaged with said positioning unit, said guide groove of each of said pedal mechanisms having a middle groove section that extends in a circumferential direction of said pivot unit, and first and second groove sections (426, 427) that extend upwardly respectively from two opposite end of said middle groove section; wherein, for each of said pedal mechanisms, when said pedal mechanism is at the close position, said positioning unit engages said first groove section of said guide groove so that said pedal mechanism is positioned at the front side of said frame body; wherein, for each of said pedal mechanisms, when said pedal mechanism is at the open position, said positioning unit engages said second groove section of said guide groove so that said pedal mechanism is positioned at a lateral side of said frame body; and wherein, for each of said pedal mechanisms, said pivot unit is operable to be moved upwardly relative to said corresponding pedal-mounting rod, so that said positioning unit is disengaged from one of said first and second groove sections (426, 427) and engages said middle groove section so as to permit relative rotation between said pivot unit and said corresponding pedal-mounting rod for movement of said pedal mechanism between the close position and the open position. a chair frame mechanism including a frame body, and two pedal-mounting rods that are disposed at a front side of said frame body; and two pedal mechanisms respectively mounted to said pedal-mounting rods, each of said pedal mechanisms being able to be positioned relative to said corresponding pedal-mounting rod at a close position and an open position, each of said pedal mechanisms including a pivot unit that is sleeved on said corresponding pedal-mounting rod and that is rotatable about and movable along said corresponding pedal-mounting rod, a positioning unit that is mounted to said corresponding pedal-mounting rod, that partially projects out of an outer surface of said corresponding pedal-mounting rod, and that engages said pivot unit, and a pedal unit that is mounted to said pivot unit, said pivot unit of each of said pedal mechanisms having a guide groove that is formed in an inner surrounding surface thereof and that is slidably engaged with said positioning unit, said guide groove of each of said pedal mechanisms having a middle groove section that extends in a circumferential direction of said pivot unit, and first and second groove sections (426, 427) that extend upwardly respectively from two opposite end of said middle groove section; wherein, for each of said pedal mechanisms, when said pedal mechanism is at the close position, said positioning unit engages said first groove section of said guide groove so that said pedal mechanism is positioned at the front side of said frame body; wherein, for each of said pedal mechanisms, when said pedal mechanism is at the open position, said positioning unit engages said second groove section of said guide groove so that said pedal mechanism is positioned at a lateral side of said frame body; and wherein, for each of said pedal mechanisms, said pivot unit is operable to be moved upwardly relative to said corresponding pedal-mounting rod, so that said positioning unit is disengaged from one of said first and second groove sections (426, 427) and engages said middle groove section so as to permit relative rotation between said pivot unit and said corresponding pedal-mounting rod for movement of said pedal mechanism between the close position and the open position.