An electroless plating process is performed on an Al layer, which is made of aluminum or an aluminum alloy, with an electroless plating liquid which is alkaline and contains a complexing agent. A plating method includes preparing a substrate 10 having a surface (for example, bottom surface of TSV 12) at which an Al layer 22 made of aluminum or an aluminum alloy is exposed; forming a zincate film 30 on a surface of the Al layer by performing a zincate treatment on the substrate; and forming a first electroless plating layer (for example, Co barrier layer 14a) on the surface of the Al layer with an electroless plating liquid (for example, Co-based plating liquid) which is alkaline and contains a complexing agent.