Abstract: The present invention relates to: an anti-fibroblast growth factor receptor 3 (FGFR3) antibody or antigen-binding fragment thereof; a nucleic acid encoding same; a recombinant expression vector comprising the nucleic acid; a host cell transfected with the recombinant expression vector; a method for producing the antibody or antigen-binding fragment thereof; a bispecific or multispecific antibody comprising the antibody or antigen-binding fragment thereof; an immune cell-engaging bispecific or multispecific antibody comprising an scFv comprising an scFv of the antibody and a second binding domain comprising at least one scFv of an antibody that binds to an immune cell-activating antigen; an antibody-drug conjugate (ADC) in which the antibody or the antigen-binding fragment thereof is bound to a drug; a chimeric antigen receptor (CAR) comprising the scFv of the anti-FGFR3 antibody as an antigen-binding site of an extracellular domain; an immune cell having the chimeric antigen receptor introduced thereinto; a c