To provide a method capable of manufacturing a high-performance plate fin type heat sink of a structure that the pitch between the fins of the plate fins of the heat sink is narrow and the thickness of the fins is thin at low cost.

The manufacturing method of a plate fin type heat sink having an excellent heat dissipation property is performed by a method wherein the plate fin type heat sink of a structure that a plurality of flat plates are vertically provided in parallel to each other on one surface of an aluminium substrate by pushing out or machining aluminium is molded. Thereafter, the heat sink is immersed into a strong alkali aqueous solution or a strong acid aqueous solution, and the thickness of the fins of the plate fins of the heat sink is reduced by the dissolution of the fins due to the strong alkali or strong acid aqueous solution.