Objectives This study investigated the relationship between oral high-risk HPV (HR HPV) infection and sexual behavior in Japanese medical professionals. Materials and methods We collected oral specimens and a self-administered questionnaire from 234 men and 171 women. Results The oral HR HPV infection prevalence was 4.7% (95% confidence interval [CI]: 3.0-7.2]) overall, 7.3% (95% CI: 4.6-11.3) for men, and 1.2% (95% CI: 0.3-4.2) for women. The number of sex partners had a significant influence on this prevalence, with variation by type of sexual behavior. The prevalence of oral HR HPV infection was significantly higher (p < 0.0001) among those with more than 20 lifetime overall sex partners (23.8%, 95% CI: 13.5-38.5) or oral sex partners (25.0%, 95% CI: 14.2-40.2). In terms of the number of vaginal sex partners, the prevalence was approximately the same for those with 6-10 (8.3%, 95% CI: 3.9-17.0), 11-20 (11.1%, 95% CI: 5.2-22.2), or more than 20 (11.5%, 95% CI: 4.0-29.0) partners (p = 0.0043). Furthermore, dividing the number of vaginal and oral sex partners into four categories (both>5, only vaginal>5, only oral>5, and both≤5), the infection prevalence was significantly higher when both vaginal and oral sex partners were more than five (12.5%, 95% CI: 7.7-19.6). The prevalence was also higher for those who had more oral than vaginal partners, compared with other groups (13.5%, 95% CI: 6.7-25.3). Conclusions and clinical relevance Oral HR HPV infection in Japan seems to be influenced by sexual behavior, and preventive health efforts such as vaccination and health education should be implemented.