Abstract: An object of the present invention is to provide a dispersion of a zirconium element-containing metal oxide having high transparency and low viscosity even at high concentration. The present invention relates to a method of producing a zirconium element-containing metal oxide dispersion, and the production method includes a step of heating a slurry containing a zirconium element-containing compound as a metal element-containing compound to perform a hydrothermal reaction, in which the heating in the hydrothermal reaction step is performed at a temperature rising rate of 90° C./hour or more.

Abstract: The present invention provides a zirconium element-containing resin composition capable of achieving both high transparency and a high refractive index. The present invention is a zirconium element-containing resin composition containing a zirconium element-containing metal oxide (A); a dispersant (B); and a polymerizable resin (C), in which the zirconium element-containing metal oxide (A) has an average particle diameter of 20 nm or less as measured by a dynamic light scattering method, and the dispersant (B) contains a compound represented by the following formula (1), the zirconium element-containing resin composition may contain a silane coupling agent, and a content ratio of the silane coupling agent is less than 30 parts by mass with respect to 100 parts by mass of a total of the compound represented by the formula (1) and the silane coupling agent.