A portable biomass stove includes a tubular seat unit and an insulation unit. The tubular seat unit includes an inner tubular seat and an outer tubular seat. The outer tubular seat surrounds the inner tubular seat, cooperates with the inner tubular seat to define an internal space therebetween, and is formed with an air inlet located under the tubular body. A top end portion of the outer tubular seat is connected to a top end portion of the tubular body in a sealing contact manner. The insulation unit is disposed in one of the internal space and an ambient space outside the outer tubular seat so as to prevent dissipation of heat out of the outer tubular seat.