PROBLEM TO BE SOLVED: To provide a method for efficiently recycling organic matter waste liquid as useful resources at a low cost, specifically an efficient circulating type treatment method in consideration of an environment utilizing the organic matter waste liquid.SOLUTION: This method for treating the organic matter waste liquid uses calcium silicate for the treatment of the organic matter waste liquid. As a preferred form, an organic matter waste liquid treatment process 10 includes a methane fermentation process 3 for fermenting methane from the organic matter waste liquid； a solid-liquid separation process 4 for separating an organic matter residue after fermenting methane from the organic matter waste liquid, into solids and liquid； and a drying process 5 for drying a solid content after solid-liquid separation. As a more preferred form, the process 10 further includes a hydrothermal synthesis process 1 for carrying out hydrothermal synthesis of the calcium silicate.
