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, and x, a, b and m are values that satisfy the following conditions, 0.18≦x≦0.4, 0.5≦a