An alumina ceramic composition to provide a low dielectric loss in the high frequency region upon sintering, which consists essentially of: 100 parts by weight of a base composition containing therein Al.sub.2 O.sub.3, CaO and TiO.sub.2 within their respective compositional range; and 0.03 to 3 parts by weight of La.sub.2 O.sub.3. The base composition is within a range A-B-C-D-E-A in the ternary diagram (Figure) in molar fraction:______________________________________ Al.sub.2 O.sub.3 CaO TiO.sub.2 ______________________________________ A 99.0 0.5 0.5 B 94.5 3.7 1.8 C 90.0 7.0 3.0 D 90.0 2.0 8.0 E 94.5 1.3 4.2 ______________________________________