Caster with a Circularly Positioning Structure

For a caster with a circularly positioning structure, stepping on the pedal can drive the driving rod and the driving piece to rotate, so that the positioning pin of the driving piece cyclically proceeds the first positioning point, the second positioning point and the path point of the positioning member, thereby driving the cam unit to push against the shaft to let the positioning piece and the orienting hole to be engaged or disengaged from each other, and let the locking end of the locking member to be engaged in or disengaged from the locking groove. In this way, the caster can selectively be locked to stop rotation, and be released to freely rotate.