The present invention relates to a carboxylation catalyst, which catalyzes carboxylation of a furan-based compound containing a hydroxyl group and a carbonyl group or a derivative thereof to prepare 2,5-furandicarboxylic acid (FDCA), and is configured as a spinel support, and noble metal nanoparticles incorporated into the spinel support selected from the group consisting of MnCo2O4, CoMn2O4, and combinations thereof, and to a method of preparing 2,5-furandicarboxylic acid (FDCA), including providing a carboxylation catalyst configured such that noble metal nanoparticles are incorporated into a spinel support; and carboxylating a furan-based compound containing a hydroxyl group and a carbonyl group or a derivative thereof in the presence of the carboxylation catalyst.