PURPOSE: To purify sewage in a short time by using the title sewage purifying device provided with a water tank, a microbe fixing bed consisting of a porous ceramic having open cells, a spacer for supporting the microbe fixing bed with a gap in between, a frame, and an air supply device.

CONSTITUTION: The microbe fixing contact material 2 is set in the water tank 2 having a sewage inlet 6 and a treated-water outlet 7. The contact material 2 is formed by the microbe fixing bed 3, the spacer 4, and the frame 5. The fixing bed 3 is made of a porous ceramic material having open cells, and the microbes are fixed therein. The spacers 4 are regularly arranged to space the fixing beds 3, and supported by the frame 5 in the form of a cube, etc. The air supply device is arranged to supply air from the lower part in the water tank 1. Since the porous fixing beds 3 of regular size are housed in the contact material 2 in the sewage purifying device of such a structure, the number of the fixing beds 3 to be housed in the volume occupied by the contact material 2 can be easily obtained, and hence the design calculation can be facilitated.