There is provided a method for stably producing metal oxide solid solution particle at low temperature, wherein an alkaline zirconia sol is used as a raw material which is mixed with a metal compound, and then dried and fired. Specifically, there is disclosed a method for producing metal oxide particle (A3) such as zirconia particle in which metal oxides are solid-solubilized, comprising: a step (I) for obtaining metal oxide (A2) sol such as zirconia sol containing a precursor of a metal oxide by mixing an alkaline zirconia (A1) sol which is obtained by a method including a step (i) for heating a zirconium salt (B2) at 60-110° C. in an aqueous medium containing a carbonate of quaternary ammonium and a step (ii) for performing a hydrothermal treatment at 110-250° C., with a compound (B1) containing an element selected from a group consisting of the group II and group III elements of the periodic table; and a step (II) for drying the thus-obtained sol and then firing a resultant substance at a temperature of 500-1200° C.