A polyolefin material can be adhered to other material with good adhesion durability by 1) applying a first primer which contains i) a resin comprising a backbone of hydrocarbon chains and/or polybutadiene chains, and ii) a polyisocyanate compound or an alkoxysilane compound, to the surface of a polyolefin material, 2) applying a second primer which contains a polyisocyanate compound or an alkoxysilane compounds, onto the layer of the first primer, and 3) adhering the surface of the polyolefin material to which the first and second primers are applied to other material using a moisture-curing polyurethane adhesive.