A fluid flow control structure for a bicycle device is basically provided with a main body, at least one port and a plug. The main body has a first chamber, a second chamber and a third chamber. The at least one port is in fluid communication with the first chamber. The plug is moved toward a first axial direction to close the port, and is moved toward a second axial direction that is opposite the first axial direction to open the port. The plug includes a dividing portion dividing the second chamber and the third chamber such that the third chamber widens as the plug moves to close the port and the third chamber shrinks as the plug moves to open the port. The plug includes a passage fluidly connecting the first chamber to the third chamber.