Adamantane compound is obtained by isomerizing a tricyclic saturated hydrocarbon having 10 to 14 carbon atoms in the presence of an X- or Y-type zeolite catalyst subjected to ion exchange with one or two kinds of metal ions selected from the group consisting of ions of rare earth metals, calcium and magnesium. The preferred catalyst is a catalyst which is further loaded with 1 to 4 kinds of metals selected from the group consisting of germanium, platinum, rhenium, nickel, cobalt, copper, iron ruthenium and rhodium. This isomerization reaction is preferably carried out in the presence of hydrogen gas.