The present invention relates to a catalyst for reforming that is employed when preparing a synthetic gas by reacting hydrocarbon such as methane with a reforming agent such as water, carbon dioxide, oxygen, air or the like. The present invention further relates to a process for producing a synthetic gas employing this catalyst for reforming. By employing the catalyst for reforming that is a mixed oxide having the composition expressed by the following formula in which the M and Co are in a highly dispersed state, it is possible to suppress precipitation of carbonaceous matters (carbon) when producing the synthetic gas. aM.bCo.cMg.dCa.eO (Where, a, b, c, d, and e are molar fractions, a+b+c+d=1, 0.0001≦a≦0.10, 0.0001≦b≦0.20, 0.70≦(c+d)≦0.9998, 0