The invention discloses a photosynthetic bacteria culture-photofermentative hydrogen production combined reactor and a method for producing hydrogen by using the same. The combined reactor comprises acylinder body and a box body, wherein the cylinder body consists of a top plate, a bottom plate and a cylindrical side wall, a first cylindrical partition and a second cylindrical partition are sequentially arranged in the cylinder body from outside to inside, so that a photosynthetic bacterium culture area, a heat preservation illumination area and a photo-fermentative hydrogen production area are sequentially formed from outside to inside; the first partition and the second partition are sequentially arranged in the box body from left to right, so that a growth medium chamber, a clean waterchamber and a hydrogen production substrate chamber are sequentially formed from left to right, the growth medium chamber is communicated with the photosynthetic bacterium culture area through a hose, the clean water chamber is communicated with the heat preservation illumination area through a hose, and the hydrogen production substrate chamber is communicated with the photo-fermentative hydrogen production area through a hose. According to the invention, a set of illumination and heat preservation device can be shared for photosynthetic bacterium culture and photo-fermentative hydrogen production, and maximum utilization of light energy and heat energy is realized.