To provide a culture apparatus for aerobic microorganisms that can efficiently culture aerobic microorganisms in a high density with a low operating cost and easy operation control and achieves the high-load operation and a method of culturing an aerobic organism using the apparatus.

The carriers for accumulating the cells of a microorganism thereon are fluidized in the culture tank 1 whereby the cells of the microorganism are immobilized on the carrier, resultantly the cells of the microorganism are accumulated in the culture tank 1. The culture tank 1 is equipped with a partition plate 2 for forming a circuit flowing pass including the upward- flowing pass 10 and the downward-flowing pass 11, a straightening vane 3 that is attached in front of the exhaust port 9 for the treated solution and is inclined downward so that the depth from the liquid face may become larger toward the wall face of the culture tank 1, an inclined bottom face 4 that is inclined so that the liquid depth may become larger from the wall face of the culture tank 1 opposing to pass partition plate 2 toward the upward flow pass 10 and the upward flow pass 10 and the downward flow pass are equipped with an oxygen feeder, respectively.