Organic-inorganic hybrids composed of organic polymer and apatite is quite attractive as novel bone-repairing materials since it has mechanical performance analogous to those of natural bone as well as bone-bonding ability, i.e. bioactivity. To fabricate such an apatite-polymer hybrid, biomimetic process has been recently paid much attention. In this process, bone-like apatite is deposited on the surfaces of organic substrates in simulated body fluid (SBF, Kokubo solution) having ion concentrations analogous to those of human extracellular fluid or more concentrated solutions. Previous studies showed that the apatite deposition is triggered by a catalytic effect of carboxyl groups (COOH) on the surfaces of the organic substrates. In this study, we examined apatite deposition on natural polypeptides derived from crops in a biomimetic solution. We selected gluten derived from wheat and zein derived from corn. Both of gluten and zein formed bone-like apatite on their surfaces in a solution that has inorganic ion concentrations 1.5 times those of simulated body fluid, when they were treated with 1 mol/L calcium chloride solution. High content of acidic amino acids such as glutamic acid and aspartic acid in gluten and zein would give large amount of carboxyl groups effective for the apatite nucleation.