The invention is related to the preparation of low-tar syngas from organic wastes and optionally to the preparation of methanol from the syngas or from the separated carbon dioxide. The process is characterized by introducing the secondary raw material comprising preferably solid communal waste, sludge and/or biomass waste into a double-flow one-body generator, comprising an inner pyrolysing, oxidizing and reducing zone and converting the obtained pyrolysis coke, pyrolysis water and tar formed by the aid of the heat content of the gas flowing upwards in the outer gas space by blowing oxygen into the fix-bed, to a raw syngas comprising carbon dioxide, carbon monoxide and hydrogen, on the fix bed of the pyrolysis coke and optionally a liquid containing liquid hydrocarbons or a powder of high carbon content are added in order to control the temperature and hydrohalides are removed from the obtained raw syngas on a calcium carbonate bed at 200-700° C., the heat content of the raw syngas is utilized, carbon dioxide is removed by a method known per se, and carbon dioxide is converted to methanol by using an external hydrogen source and optionally the obtained syngas is also converted to methanol by a method known per se.