A voice coil assembly capable of realizing a flat thin loudspeaker having a high efficiency, reduced divided vibrations, a flat frequency response, and reduced operation defects. The voice coil assembly includes a plurality of internal-winding voice coils, each including a rectangular bobbin having a rectangular cross section and defining a rectangular space therein and an internal rectangular coil fixed to an inner wall surface of the rectangular bobbin defining the rectangular space, wherein an outer wall surface of the rectangular bobbin of one internal-winding voice coil is adhered and fixed to an outer wall surface of the rectangular bobbin of another internal-winding voice coil.