RNA extraction is essential for reverse transcription (RT) PCR or RT real-time PCR to detect many viral pathogens in various samples. Owing to the lack of cell culture methods of norovirus, only molecular methods have been applied to the detection of norovirus. In the notification of the Ministry of Health, Labour and Welfare, a column method is exemplified for the extraction of RNA from various samples, so extraction of nucleic acid by column method is performed generally. We compared a column method and a magnetic bead method in terms of the RNA extraction efficiency from fecal, oyster and sewage. RT real-time PCR was used for the evaluation of RNA extraction efficiency. The norovirus concentration in oyster and sewage samples was significantly higher when the magnetic bead method was used (p<0.01). It was found that the magnetic bead method is superior for RNA extraction from oyster and sewage samples, and it gives higher RNA yield than the column method.