| Locality | Post Code |
|---|---|
| Hoshodai (大分市) | 870-0171 |
| Hoso (大分市) | 870-0305 |
| Ichi (大分市) | 870-1151 |
| Ichigi (大分市) | 870-0316 |
| Ichino (大分市) | 870-0312 |
| Ichinosu (大分市) | 870-0112 |
| Iejima (大分市) | 870-0113 |
| Ikushi (大分市) | 870-0003 |
| Ikushi Minatomachi (大分市) | 870-0001 |
| Imaichi (大分市) | 870-1223 |
| Imazuru (大分市) | 870-0938 |
| Ino (大分市) | 870-0134 |
| Irikura (大分市) | 870-1202 |
| Isshakuya (大分市) | 879-2203 |
| Iwatamachi (大分市) | 870-0936 |
| Izumimachi (大分市) | 870-0041 |
| Joharu (大分市) | 870-0267 |
| Jonamminamimachi (大分市) | 870-0825 |
| Jonankitamachi (大分市) | 870-0827 |
| Jonannishimachi (大分市) | 870-0826 |
| Jonanyamatedai (大分市) | 870-0828 |
| Jotomachi (大分市) | 870-0922, 870-0153 |
| Kaiwara (大分市) | 870-0107 |
| Kaku (大分市) | 870-0877 |
| Kakukita (大分市) | 870-0848 |
| Kakuminami (大分市) | 870-0849 |