This invention provides a carrier for a synthesis gas production catalyst that can suppress carbon depositions and allows to efficiently produce synthesis gas on a stable basis for a long duration of time when producing synthesis gas by carbon dioxide reforming. It is a carrier to be used for producing synthesis gas containing carbon monoxide and hydrogen from source gas containing methane-containing light hydrocarbons and carbon dioxide. The carrier contains magnesium oxide grains and calcium oxide existing on the surfaces of magnesium oxide grains. The calcium oxide content thereof is between 0.005 mass% and 1.5 mass% in terms of Ca.