Porcine noroviruses have been previously reported by some Japanese research groups. However, there is limited information regarding their epidemiology and pathogenicity in pigs. Here, we attempted to determine the frequency of norovirus infection in pigs in Japan. Fecal samples were collected from 190 healthy pigs in the Tokai region of Japan and checked for noroviruses by reverse transcription-PCR. Noroviruses were present in 11 of the 190 fecal samples (5.8%) and were genetically related to the porcine noroviruses previously detected in other regions of Japan. Our data suggest that porcine noroviruses are circulating among populations of healthy pigs without clinical signs in Japan.