Abstract: A method of producing long size preform is disclosed in which: a long size cylindrical collector extended in a manner penetrating a chamber is moved lengthwise thereof while it is rotated; a preheated metal layer is formed on the outer periphery of the collector by adhering a molten metal to the collector within the chamber at the upstream side in the traveling direction of the collector; and a molten metal is caused to be cumulated by spray deposit on the metal layer formed on the outer periphery of the collector by spraying the molten metal from the ceiling within the chamber at the downstream side in the traveling direction of the collector by way of an atomizer which ejects an inert gas. By using this method, porosity occurring on the collector side of the preform may be inhibited.