Recently, Avian bornavirus (ABV) was detected in proventricular dilatation disease (PDD) affected-birds and feather picking diseases affected-birds. However, the pathogenicity of ABV has not been thoroughly investigated. In this study, we surveyed ABV in pet birds in Japan. We found four ABV-infected birds among 93 pet birds using RT-PCR, and genotypes of the ABV were determined as ABV-2 and -4. Two of the birds positive for ABV-4 showed proventricular dilatation typically found in PDD, and chronic stomach disturbance, whereas two of the birds positive for ABV-2 showed unexplained behavioral problems that are tapping, autophagia, and cloaca prolapse.