PROBLEM TO BE SOLVED: To suppress a trouble during storage of biomass by sterilizing the biomass at low cost.SOLUTION: A biomass treatment apparatus 100 includes a heating furnace 110 for heating biomass A (first biomass) which is biomass derived from agricultural waste such as EFB, PKS, barley straw or rice straw up to a temperature (for example, 150°C or higher or below 200°C) determined beforehand, and a contact part 120 for bringing volatile gas generated from the heating furnace 110 into contact with biomass B (second biomass).SELECTED DRAWING: Figure 1