To provide a new material for inhibiting the proliferation of a vacuolating toxin-producing bacterium (Helicobacter pylori).

The agent for inhibiting the proliferation of the vacuolating toxin-producing bacterium contains an extract from a fired shell. Preferably, the extract is contained in a proportion of ≥10% in a solvent in the agent for inhibiting the proliferation of the vacuolating toxin-producing bacterium. Preferably, the shell is the one of scallop.