A periodic mid-infrared broadband chiral structure is proposed, in which each unit is composed of four indium tin oxide (ITO) helical subunits in different rotating directions. The simulation results show that the flat-topped broadband circular dichroism (CD) can be achieved in the mid-infrared waveband by optimizing the number of helical turns, the helical radius, the pitch of helix, and the wire radius of helix. Compared with the two non-rotating helical structures, the CD band of the ITO rotating helical structure is found to be broader. At the wavelength of 7.95 μm, for the ITO rotating helical structure, the maximum value of CD is 0.454 and the full width at half maximum (FWHM) of CD is 7.5 μm in the wavelength ranging from 4.1 to 11.6 μm. The broadband CD is caused by the strong coupling among the four ITO helical subunits in different rotating directions. The simulation results also show that compared with the gold and silver rotating helical structures, the proposed structure exhibits evidently better broadband CD, which provides a new idea for the design of broadband polarization state control devices in the mid-infrared band.