NOVELTY - A biomass material is supplied to composite gasification furnace and pyrolysis is carried out to generate volatile gas and solid coke. A portion of coke is oxidized in coke gasification portion. The reaction gas with fine coke grain released from the pyrolysis region, tar heavy constituent and catalyst are partially oxidized. The tar heavy constituent is thermally and catalytically cracked and converted into lightweight combustible gas. The unreacted coke and catalyst fine grain are separated into gas and solid. Thus, composite gasification of biomass is enabled.    USE - Composite gasification of biomass.    ADVANTAGE - The method enables easy and steady gasification of biomass, at high gasification rate and with low coke content.    DETAILED DESCRIPTION - A biomass material is supplied into composite gasification furnace from feeding orifice in pyrolysis region and pyrolysis is carried out 500-600 degrees C to generate volatile gas and solid coke. A portion of coke is made to flow into coke gasification portion in the furnace and oxidized with primary gasification agent such that temperature of the gasification portion is 1000 degrees C to generate combustible gas. The high temperature gas which flows from the upstream of the gasification portion is used as heat required for pyrolysis of biomass. The temperature of the pyrolysis region is maintained at 500-600 degrees C. The reaction gas with fine coke grain released from the pyrolysis region, tar heavy constituent and catalyst which flows from upstream of gasification portion are subjected to partial oxidation by secondary gasification agent. The temperature of heavy constituent is made into more than 1000 degrees C. The tar heavy constituent is subjected to thermal cracking and catalytic cracking by the high temperature and catalyst, and converted into lightweight combustible gas. The unreacted coke in the heavy constituent gasification portion and catalyst fine grain in the gas are supplied to cyclone separator and separated into gas and solid. The flue gas is exhausted through the cyclone separator and solid grain is sent to coke gasification portion through lower circumference of the cyclone separator. Thus, composite gasification of biomass is enabled. An INDEPENDENT CLAIM is included for composite gasification device.