A process of manufacturing a taper leaf spring by which rollers for measuring the length and the thickness are respectively disposed on the take-out side of a material plate for a taper leaf spring relative to a pair of rolling rollers, and also rollers for measuring the breadth are disposed on the same take-out side; rolling for regulating the breadth is beforehand performed by a pair of edge rollers on the take-in side of the material plate relative to the pair of rolling rollers; the distance of the interval between both rolling rollers is adjusted by comparing signals coming from the rollers for measuring the length and the thickness with the standard signals based on the predetermined specifications of the length and the thickness; the regulation of the breadth by means of the pair of edge rollers is controlled by comparing the signal from the breadth measuring rollers with the standard signal based on the predetermined specification; so that the material plate is rolled to a taper as desired.