PURPOSE: To manufacture the preform in dissimilar plate shape with good efficiency by simultaneously combining the rocking angle of an atomizer and the movement in one direction of a collector.

CONSTITUTION: A molten metal is atomized by spraying the high pressure gas of low temp. injected from an atomizer 4 to the molten metal 2 slenderly flowed down from the nozzle 3 of a tandish 1 and accumulated by rapidly cooling in a collector 6 to manufacture a semi-solidified or solidified preform 5. In this case, the atomizer 4 is rocked at some resting period in the width B direction of the preform and the collector 6 is moved at constant speed in one direction orthogonal with the width direction as well to form the preform 5 in various plate shapes.