The hyperfine structure of the ground state of the lithium-like scandium ion (Z = 21) is considered. The effects of electron-electron interaction are taken into account in the first order in 1/Z using the quantum electrodynamic perturbation theory and in higher orders using the method of configuration interaction in the Dirac-Fock-Sturm basis. One-loop radiative corrections are calculated in all orders in αZ with an effective local screening potential. The corrections for the finite nuclear size and the distribution of the magnetic moment over the nucleus have been refined.