NOVELTY - The continuous fermentation apparatus comprises a source input unit (100), fermentation units including a downward fermentation tube (200) and an upward fermentation tube (300), and a microbial cell collection unit (500) formed on a lower part of the upward fermentation tube. The source input unit includes source that includes marine algae and/or cellulosic biomass and a sugar mixture. The collection unit is configured for collecting microbial cells and precipitates on a lower part of the downward fermentation tube. The fermentation tubes include an impeller and a screen (600).    USE - The apparatus is useful for fermenting a sugar mixture such as glucose, galactose, sucrose and/or xylose (all claimed) to produce biofuel such as ethanol.    ADVANTAGE - The apparatus allows continuous fermentation of the sugar mixture in a simple and a rapid manner without any shock.    DETAILED DESCRIPTION - The continuous fermentation apparatus comprises a source input unit (100), fermentation units including a downward fermentation tube (200) and an upward fermentation tube (300), and a microbial cell collection unit (500) formed on a lower part of the upward fermentation tube. The source input unit includes source that includes marine algae and/or cellulosic biomass and a sugar mixture. The collection unit is configured for collecting microbial cells and precipitates on a lower part of the downward fermentation tube. The fermentation tubes include an impeller and a screen (600). The microbial cells collected by the microbial cell collection unit of the upward fermentation tube are supplied into the downward fermentation tube to be recycled. An INDEPENDENT CLAIM is included for a multi-step continuous fermentation process of sugar mixture using a continuous fermentation apparatus.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a continuous fermentation apparatus.    Source input unit (100)    Downward fermentation tube (200)    Upward fermentation tube (300)    Collection unit (500)    Screen. (600)