||Azospirillum sp. B510 was inoculated to rice seedlings, and transplanted into a paddy field. The rice growth was significantly increased by the inoculation. Principal coordinate analysis of bacterial communities in rice tissues by 16S rRNA gene showed that whole communities were not changed by B510 inoculation. However, the abundance of Veillonellaceae and Aurantimonas significantly increased in basal parts and shoots of B510-inoculated plants compared with uninoculated control, respectively. The abundance of Azospirillum (0.02-0.5%) was not different between B510-inoculated and uninoculated plants. One possible explanation is that B510 inoculation altered abundance of specific community members in rice, which stimulated rice growth.