The hyperfine coupling constants of the proton dripline odd-odd 40 Sc nucleus were deduced from the hyperfine spectrum of the 3d4s 3 D2 ↔ 3d4p 3 F • 3 transition in Sc II, measured by the bunched beam collinear laser spectroscopy technique. The ground state magnetic dipole and electric quadrupole moments were determined for the first time as µ = +5.57(4)(2) µN and Q = +42(38)(28) e 2 fm 2 , respectively. The magnetic moment is well reproduced by the additivity rule with magnetic moments of neighboring odd-even nuclei in the vicinity of the doubly-magic 40 Ca nucleus. An ab-initio multishell valence-space Hamiltonian was also employed to calculate the magnetic moment of 40 Sc, which spans across the sd and f p nuclear shells, where we obtained good agreements.