The present invention relates to a production method for efficiently obtaining an acrylic acid-based polymer having a narrow molecular mass distribution and a low molecular mass, without using a large amount of chain transfer agent. A method for continuously producing an acrylic acid-based polymer obtained by continuously polymerizing a monomer having acrylic acid as an essential component, characterized in that a liquid feed pump applies a mechanical load of 0.5 to 2.5 kJ/L to the liquid discharged from the outlet of a reactor. An acrylic acid-based polymer having fewer high-molecular-mass components, excellent dispersion and other properties, and a low molecular mass is thereby obtained.