A novel particulate composite hydrotalcite which offers antacidic effect comparable to that of a particulate hydrotalcite so far used as a gastric antacid and, further, offers excellent stomach inner wall protection effect. A particulate composite hydrotalcite represented by the following formula (1),(MgaZnb)1-xAlx(OH)2(An−)x/n.mH2O (1)wherein An− is CO32−, SO42− or Cl−, n is 1 or 2, andx, a, b and m are values that satisfy the following conditions,0.18≦x≦0.4, 0.5≦a<；1, 0<；b≦0.5, 0≦m<；1,and a gastric antacid using the particulate composite hydrotalcite as an effective component. When used as a gastric antacid, the particulate composite hydrotalcite suppresses the occurrence of damage in the mucous membranes of stomach and intestines.
