Ammonia synthesis catalyst

A metal-carrier material comprising a composite oxide comprising an oxide of a metal element L and an oxide of a metal element N, the composite oxide represented by a composition of general formula (1):

• LnN1-n (1)
• the composite oxide having the following characteristics (a) to (d):
• (a) the metal element L being an oxide of any element(s) selected from the group consisting of Ba and Sr,
• (b) the metal element N comprising a Group 1 or Group 2 element other than the metal element L,
• (c) n of 0.001 or more and 0.300 or less, and
• (d) the oxide of the metal element L and the oxide of the metal element N forming no solid solution, and oxide particles of the metal element L being deposited on surfaces of oxide particles of the metal element N,
• the composite oxide having, supported thereon, particles of at least one metal M selected from the group consisting of Ru, Fe, Co, Ni, Rh, Pd, Os, Ir, and Pt,
• wherein the metal particles M are supported on the oxide of the metal element L and oxide of the metal element L are deposited on surfaces of the metal particles M,
• and wherein the metal particles M are not in direct contact with the oxide of the metal element N.