Provided is a planar focusing grating coupler, comprising: a light waveguide including a cladding layer and a core layer formed on a substrate and maintaining incident laser light in a single mode; and a focusing grating coupler formed to have a predetermined grating pitch at a certain area over the core layer, wherein the light using to the light waveguide forms a focal point with the grating layer in the direction perpendicular to the focusing grating coupler, whereby an ultra small pickup head for a mobile optical disk can be used.