An electronic device for a motor vehicle includes a metal tubular casing extending longitudinally and opening at its two ends, and a wall having a curved profile with cooling fins on its outer surface. The electronic device includes an assembly of printed circuit boards comprising a first plurality of printed circuit boards that include heat-generating electronic components. The printed circuit boards of the assembly are connected together by flexible conductive elements. The device further comprises a first heat sink arranged inside the tubular casing comprising a curved wall generally extending parallel to the curved wall of the tubular casing. The first plurality of printed circuit boards is interposed between the curved inner surface of the wall of the casing and the curved wall of the first heat sink so heat is dissipated through the first heat sink and through the curved wall equipped with cooling fins of the tubular casing.