A food material capable of suppressing the genesis of breast cancer or proliferation of terminal breast cancer. An extract of Agaricus Blazei Murill comprising an ingredient capable of suppressing the genesis of breast cancer or proliferation of terminal breast cancer is provided. This ingredient can be a chromatographic main elution fraction of 100 to 2000 molecular weight obtained through the steps of extracting the fruit body of Agaricus Blazei Murill with hot water, dialyzing the obtained extract and subjecting the obtained dialysis external fluid to chromatography. Alternatively, the above ingredient can be a dialysis external fluid obtained through the steps of extracting the fruit body of Agaricus Blazei Murill with hot water, adding ethanol to the obtained extract to thereby obtain precipitates, and dissolving the precipitates in water and dialyzing the resultant solution.
