Abstract: Atomizer for viscous fuels formed by a first and a second mixing chamber arranged along a common longitudinal axis, the second chamber being formed by a cylindrical portion and two consecutive frustoconical portions on the conical walls of which two rows of orifices are placed for the inlet for the atomized fuel into the combustion chamber. The orifices are arranged according to two circumferences and have axes orthogonal to the conical walls on which they are placed, axes which meet inside the second mixing chamber at a point on the longitudinal axis. The orifices are equally angularly spaced and radially aligned. The angle between the axes of two orifices symmetrical with respect to the longitudinal axis of the outer row is comprised between 80.degree. and 120.degree., while the difference between this angle and the corresponding angle formed by the axes of the two symmetrical orifices of the inner row is not less than 20.degree..