An improved fuel oil atomizer which comprises a burner tube through which fuel oil is supplied under selected pressure, and a coaxial surrounding steam tube providing an annular space therebetween, the flow of steam being under greater pressure than the oil pressure. A burner head is joined to the burner oil tube through an orifice of selected diameter. The burner head has a long axial bore of constant selected diameter, which leads to the burner tip, which has a plurality of tip ports. There are a number of transverse ports between the annular steam path and the central bore, so that the steam can flow under pressure into the central bore of the burner head to mix thoroughly with the pressurized oil flowing from the orifice. Two factors are important in the construction of the burner head, namely that the central bore must be of constant diameter from the point where the steam and oil mix, outwardly toward the burner tip ports. Secondly, the total cross-sectional area of the tip ports must be less than the cross-sectional area of the central bore.