Antibiotics have been used in various fields such as livestock farm and fish farm as well as hospital in order to treat diseases caused by bacteria. However, the antibiotics that are not completely decomposed, but remains as residue and discharge to aquatic environment, can cause an imbalance in the gut flora of host, as well as regulate abnormal host gene regulatory system. We investigated the effects of chronic exposure with the low concentrations of erythromycin and ampicillin on gut microbiome and immune and stress-related gene expression using Korea native ricefish (Oryzias latipes). As a result of microbiome analysis, the proportion of Proteobacteria was increased in the ricefish when exposed to erythromycin and ampicillin chronically, whereas the proportion of other bacterial phyla decreased. In addition, the immune and stress-related genes were significantly influenced in the ricefish under the chronic antibiotics exposure. These results show that the internal microbial flora and the host gene expression are susceptible even in the low concentration of chronic antibiotic existing environments. This study provides the importance of the appropriate use of antibiotics dose to maintain the sustainable and healthy aquaculture industry and water ecosystem.