A gas flowrate control device for turning the flame adjustment wheel of a gas burner is disclosed to include a control wheel, which has an internal gear meshed with the flame adjustment wheel of the gas burner, a big gear surrounding the internal gear, and two small gears respectively formed integral with two sides of the big gear and surrounding the internal gear, and a handle, which has a grip and two arched clamping arms symmetrically extending from the grip and clamped on the control wheel, each arched clamping arm having two toothed arm positions respectively meshed with the two small gears of the control wheel and a crevice defined between the two arm portions for accommodating the big gear.