A polishing liquid composition includes composite oxide particles containing cerium and zirconium, a dispersing agent, and an aqueous medium. A powder X-ray diffraction spectrum of the composite oxide particles obtained by CuK.alpha.1 ray (.lamda.=0.154050 nm) irradiation includes a peak (first peak) having a peak top in a diffraction angle 2.theta. (.theta. is a Bragg angle) range of 28.61 to 29.67.degree., a peak (second peak) having a peak top in a diffraction angle 2.theta. range of 33.14 to 34.53.degree., a peak (third peak) having a peak top in a diffraction angle 2.theta. range of 47.57 to 49.63.degree., and a peak (fourth peak) having a peak top in a diffraction angle 2.theta. range of 56.45 to 58.91.degree.. A half-width of the first peak is 0.8.degree. or less.