A method of forming a hollow pole projecting from a metal plate by plastic deformation and comprising the steps of: (a) pressing the plate from one surface of the plate using a press tool so as to form a hole on the one surface and a projection on the other surface thereof; (b) moving metal of the plate around said projection towards interior of said hole so as to gather the metal into a periphery of an opening of said hole using a tapered tool; (c) pressing said periphery of said hole using a flat press tool which is greater than said projection in an external diameter so as to move the metal gathered by said tapered tool further towards the interior of said hole and to increase a height of said projection; and (d) inserting said press tool into said hole while pressing the interior of said hole so as to increase further the height of said projection and to form the hollow pole. The projection can therefore be made substantially higher with respect to the thickness of the plate or the thickness of the hollow pole can be made thicker. Further, a heatsink utilizing the hollow poles as superior heat dissipating fins can be manufactured easily and cheaply.