A method for patterning a plastic surface (1 ), in which the surface is provided with an area different from the material of the surface by the following measures: - a coating (2) is formed onto a plastic surface (1 ) of themoplastic polymer using thermoplastic polymer dissolved or dispersed in water, by applying the water solution or dispersion onto the plastic surface (1 ) and by evaporating the water, - an activating beam (3) is directed to the plastic surface (1 ), and the surface and the activating beam are moved in relation to each other so that at the point of action (P) of the beam, a component in the plastic surface or in the coating absorbs electromagnetic radiation of the beam (3), causing the heating and fusing and mixing of the thermoplastic polymers of the plastic surface (1 ) and the coating (2) at the interface of the coating and the plastic surface to each other so that a permanent bond (4) of the polymer of the plastic surface (1 ) and the polymer of the coating (2) is formed in the range of action of the beam, and - removing the coating (2) from the area left outside the range of action of the beam, by a treatment which leaves the coating (2) more firmly attached to the surface in the range of action of the beam, on the surface.