Abstract: A fume-treating device and fume ducting system for cooker hoods is disclosed. The top section of the bottom fume passage is mounted with a top fume passage and the side of the bottom fume passage is at least a bottom fume-suction inlet, which is a detachable structure. The top section of the top fume passage corresponding to the top section of a stove is provided with a top fume suction inlet. The apparatus is suitable for use in a site where large amount of fume is discharged. The bottom fume outlet corresponding to the inner side of the fume passage is provided with a fume filter. The rising fume passes through an active carbon filter before it is discharged to the environment.