Abstract: A method of collecting biogas from organic wastes in a landfill includes a branch pipe installation step of installing a waste liquid input branch pipe and a landfill gas extracting branch pipe in the landfill, and installing a leachate extracting branch pipe under the landfill at a certain slopea fitting installation step of connecting an organic waste pretreatment device, the waste liquid input branch pipe, a landfill gas collecting pipe and the landfill gas extracting branch pipe a pretreatment step of mixing organic wastes with leachate generated from the landfill to produce a waste liquida waste liquid input step of dividing the waste liquid input branch pipe into some regions and progressively inputting and pressing the waste liquid mixed in the pretreatment step and a gas extraction step of extracting and collecting a generated landfill gas.