Heat exchanger comprising: - a plurality of tubes, arranged in a first and a second row (3A, 3B), and through which a refrigerant is intended to circulate; - a first and a second header tank (4, 5) inside which tanks the tubes of each of the said rows emerge; - a longitudinal dividing partition arranged in the first header tank to divide it longitudinally into: ▪ a refrigerant inlet compartment into which the tubes of the first row emerge; and ▪ a refrigerant outlet compartment into which the tubes of the second row emerge, - a plurality of transverse dividing partitions arranged in the second header tank to divide it transversely into a plurality of return compartments into which at least one tube of the first row and one tube of the second row emerge, - the first and second header tanks (4, 5) each comprising a bottom plate (6, 7) comprising a plurality of orifices that accept the corresponding tubes, and a cover (8, 9) attached to the said bottom plate, the cover of the first header tank taking the form of a pressed metal plate defining the inlet compartment and the outlet compartment, characterized in that: - the bottom plate of the first header tank comprises two semicircular deformations arranged respectively facing the longitudinal ends of the inlet and outlet compartments (17, 18); and - the bottom of the semicircular deformations is connected to the face of the bottom plate that faces towards the cover by an intermediate connecting zone which, in axial section, has a predetermined curvature comprising a point of inflection. - a plurality of tubes, arranged in a first and a second row (3A, 3B), and through which a refrigerant is intended to circulate; - a first and a second header tank (4, 5) inside which tanks the tubes of each of the said rows emerge; - a longitudinal dividing partition arranged in the first header tank to divide it longitudinally into: ▪ a refrigerant inlet compartment into which the tubes of the first row emerge; and ▪ a refrigerant outlet compartment into which the tubes of the second row emerge, ▪ a refrigerant inlet compartment into which the tubes of the first row emerge; and ▪ a refrigerant outlet compartment into which the tubes of the second row emerge, - a plurality of transverse dividing partitions arranged in the second header tank to divide it transversely into a plurality of return compartments into which at least one tube of the first row and one tube of the second row emerge, - the first and second header tanks (4, 5) each comprising a bottom plate (6, 7) comprising a plurality of orifices that accept the corresponding tubes, and a cover (8, 9) attached to the said bottom plate, the cover of the first header tank taking the form of a pressed metal plate defining the inlet compartment and the outlet compartment, characterized in that: - the bottom plate of the first header tank comprises two semicircular deformations arranged respectively facing the longitudinal ends of the inlet and outlet compartments (17, 18); and - the bottom of the semicircular deformations is connected to the face of the bottom plate that faces towards the cover by an intermediate connecting zone which, in axial section, has a predetermined curvature comprising a point of inflection.