Provided are: a complex oxide that exhibits high redox ability even at low temperatures, has excellent heat resistance, and stably retains these characteristics even on repeated oxidation and reduction at high temperature; a method for producing the same; and an exhaust gas purification catalyst. The inventive complex oxide contains more than 0 but no more than 20 parts by mass of Si, calculated as SiO2, per total 100 parts by mass of rare earth metal elements including Ce, calculated as oxides; and has a characteristic such that when it is subjected to temperature-programmed reduction (TPR) measurement in a 10% hydrogen-90% argon atmosphere at from 50° C. to 900° C. with the temperature increasing at a rate of 10° C./min, followed by oxidation treatment at 500° C. for 0.5 hours, and then temperature-programmed reduction measurement is performed again, its calculated reduction rate at and below 400° C. is at least 1.5%.