The present invention provides a fluorescent rare earth complex having high solubility to a medium, showing fluorescence of high intensity and possessing excellent durability, and also provides a light-emitting element using that complex. The rare earth complex comprises a rare earth ion and a phosphine oxide ligand, and the phosphine oxide ligand contains a phosphorus atom connecting to at least one phenyl group. In the phenyl group, at least one of the meta-positions is substituted. It is also necessary that the para-position of the phenyl group be not substituted.