Pathogenic microorganisms, such as bacteria and viruses, readily enter the oral cavity because it is constantly exposed to outside air, for which actions of salivary immune components functioning as the frontline defense mechanism are important. Human-β-defensin-2 (HBD-2) plays an important role in prevention of upper airway infection. It is secreted by airway epithelial cells and salivary glands and contributes to antimicrobial activity against viruses and bacteria. We previously reported that antimicrobial peptide expression is suppressed by temporary or chronic exercise stress, leading to susceptibility to upper airway infection. In this study, focusing on moderate exercise considered to increase intraoral immune function, we investigated the influence of one-year exercise training on the oral local immune function and Streptococcus mutans-suppressing effect. The salivary HBD-2 levels were 35.9±7.4 and 60.4±8.7 pg/mL before and after intervention, respectively, showing that it significantly increased (p<0.001). Regarding the Streptococcus mutans-suppressing effect, a significant bacterial growth-inhibitory effect was noted after intervention compared with that before intervention (p<0.01). Focusing on moderate exercise training considered to increase intraoral immune function, the influence of one-year exercise training on the oral local immune function and Streptococcus mutans growth-inhibitory effect was investigated.