A one-piece drainage channel for surface drainage is disclosed that comprises a molded, elongate body, in particular made of concrete polymer, with an upper surface over which vehicles can travel and which comprises inlet openings that open into a channel compartment, with side walls and a floor and with end faces to which can be connected additional drainage channels, catch pits or similar drainage installations, wherein the channel compartment comprises adjoining boundary surfaces, in particular a ceiling boundary surface nearest to the upper surface, side boundary surfaces and a base boundary surface. In order to provide easier manufacture along with high stability, even in the case of large channel widths and lengths, it is proposed to construct at least one side boundary surface and the base boundary surface or the ceiling boundary surface so that the channel compartment tapers conically in the direction from one of the end faces to the other. This allows a solid core to be used during casting of the drainage channel.