High molecular weight hyaluronic acid microparticles are provided.A composite nanoparticle according to the present invention comprises (A) hyaluronic acid and (B) a zwitterionic compound and has a particle size of 100 nm or less.本發明係提供高分子量之玻尿酸微粒子。本發明相關之複合奈米粒子為含有(A)玻尿酸及(B)兩性離子化合物且粒徑為100nm以下之複合奈米粒子。