A caster mechanism for a carriage having foot rods (a, b) includes a stopper mechanism (3) fixedly secured to a lower end of each foot rod. A wheel support mechanism (2) is rotatably positioned below the stopper mechanism, and includes an engagement bracket 1 extending parallel to the stopper mechanism. The engagement bracket has an engagement fitting portion (12) formed at a first end of an arm plate (11) having a predetermined length. The stopper mechanism also has an actuating lever (8) at a first end of a base plate (34) having a predetermined length, which is adapted to turn upwardly and downwardly about an end thereof. An engagement member (7) adapted to turn up and down in operative association with the actuating lever is positioned below the first end of the base plate. The engagement member and the engagement fitting portion are simultaneously engaged or disengaged.