To provide a manufacturing method for producing powdered articles of a low molecular weight polycarboxylic acid based polymer by a simple and efficient process.

The method for manufacturing a polycarboxylic acid based polymer includes: (i) a step of adding a monomer having 2-methyleneglutaric acid (salt) as an essential component, a solvent, and a polymerization initiator to a reactor; (ii) a step of initiating polymerization by heating and/or irradiating with light; and (iii) a step of concentrating the reaction solution to 90-100 mass% solid content and the amount of the 2-methyleneglutaric acid (salt) used based on 100 mol% all the monomers is 30-100 mol%, and the amount of the solvent used based on 100 mass% all the raw materials is 50-85 mass%.