Problem. Provided are a method for synthesizing spherical porous titanium oxide nanoparticles, which is easy to operate, does not take a long time for synthesis, and can easily adjust the particle diameter and the pore diameter of the spherical porous titanium oxide nanoparticles in accordance with the application thereof; spherical porous titanium oxide nanoparticles produced by the synthesizing method; and a gene gun carrier consisting of the spherical porous titanium oxide nanoparticles. Solution. A method for synthesizing spherical porous titanium oxide nanoparticles, includes: a step of reacting titanium isopropoxide and carboxylic acid in supercritical fluid, wherein the supercritical fluid is supercritical methanol, and the carboxylic acid is formic acid, acetic acid, benzoic acid, o-phthalic acid, fumaric acid, or maleic acid.