Abstract: To present a green- to yellow-emitting phosphor whereby a light-emitting device having high color rendering properties and high luminance can be obtained, a light-emitting device employing such a phosphor, and an image display device and a lighting system, containing such a light-emitting device. A phosphor made of a compound represented by the following formula (I), which comprises, as matrix, a compound of a garnet structure and which contains, as a luminescent center ion, a metal element in the matrix: M1aM2bXcM3dM43Oe??(I) wherein M1 is Mg and/or Zn, M2 is a bivalent metal element excluding Mg and Zn, X is a metal element as a luminescent center ion composed mainly of Ce, M3 is a trivalent metal element excluding X, M4 is a tetravalent metal element, and a, b, c, d and e are numbers satisfying the following formulae, respectively: 0.001?a?0.5 2.5?b?3.3 0.005?c?0.5 1.5?d?2.3 e={(a+b)×2+(c+d)×3+12}/2.