A chuck structure for fixing a drumstick on a non-circular revolving shaft of a foot drum includes a retractable chuck, two arched plates and a fastening element. The two arched plates clamp the non-circular revolving shaft. An inner arched surface of each arched plate has an inner fastening surface correspondingly clamping the non-circular revolving shaft, and an outer arched surface of each arched plate has a spiked surface. The retractable chuck includes a fastening portion and a rotating portion, which are pivotally connected to each other, clamp the two arched plates, and are penetrated by the drumstick. Each of the fastening portion and a rotating portion has a clamping surface abutting against the spiked surface. The fastening member propels and rotates the rotating portion, so as to allow the retractable chuck, spaced by the two arched plates, to clamp and fasten on the non-circular revolving shaft.