(D)：Difending Champion
| Date | Championships | Course | Venue | Champion | |
| 4/23 – 4/26 | Asian Tour Kirin Open Golf Championship | Ibaraki Golf Club East Course | IBARAKI | Frankie Minoza | |
| 6/25 – 6/28 |  |
31st 1998 Japan Women’s Open Golf Championship | Miyoshi Country Club West Course | AICHI | Natsuko Noro |
| 7/7 – 7/10 | 83rd 1998 Japan Amateur Golf Championship | Ono Golf Club | HYOGO | Hidemasa Hoshino | |
| 8/19 – 8/21 | 4th 1998 Japan Junior Golf Championship Boy’s 15-17 Division | Kasumigaseki Country Club East Course | SAITAMA | Yusaku Miyazato | |
| 8/20 – 8/21 | 4th 1998 Japan Junior Golf Championship Boy’s 12-14 Division | Kasumigaseki Country Club East Course | SAITAMA | Kota Tokashiki | |
| 8/20 – 8/21 | 4th 1998 Japan Junior Golf Championship Girl’s 15-17 Division | Kasumigaseki Country Club West Course | SAITAMA | Ayako Oketa | |
| 8/20 – 8/21 | 4th 1998 Japan Junior Golf Championship Girl’s 12-14 Division | Kasumigaseki Country Club West Course | SAITAMA | Ayako Uehara | |
| 8/25 – 8/28 | 52nd 1998 Japan Collegiate Golf Championship | Sodegaura Country Club Shinsode Course | CHIBA | Tomohiro Kondo | |
| 8/26 – 8/28 | 35th 1998 Japan Women’s Collegiate Golf Championship | Sodegaura Country Club Shinsode Course | CHIBA | Misato Nishikawa | |
| 10/1 – 10/4 | |
63rd 1998 Japan Open Golf Championship | Oarai Golf Club | IBARAKI | Hidemichi Tanaka |
| 10/7 – 10/9 | 40th 1998 Japan Women’s Amateur Golf Championship | Sagami Country Club | KANAGAWA | Yun-Jye Wei | |
| 10/14 – 10/16 | 20th 1998 Japan Senior Golf Championship | Gifuseki Country Club East Course | GIFU | Tetsuo Miura | |
| 10/15 – 10/16 | 5th 1998 Japan Mid-Senior Golf Championship | Gifuseki Country Club West Course | GIFU | Norito Kobayashi | |
| 10/15 – 10/16 | 5th 1998 Japan Grand-Senior Golf Championship | Gifuseki Country Club West Course | GIFU | Kinji Ando | |
| 10/22 – 10/23 | 6th 1998 Japan Women’s Senior Golf Championship | Aso Golf Club Kijima/Nakadake Course | KUMAMOTO | Akemi Minato | |
| 10/27 – 10/30 | 7th 1998 Japan Amateur Match Play Golf Championship | Naruo Golf Club | HYOGO | Taichiro Kiyota | |
| 10/27 – 10/30 | 7th 1998 Japan Women’s Amateur Match Play Golf Championship | Naruo Golf Club | HYOGO | Shiho Okano | |
| 11/11 – 11/13 | 3rd 1998 Japan Mid-Amateur Golf Championship | Ranzan Country Club | SAITAMA | Yasuyuki Ishii | |
| 11/19 – 11/20 | 3rd 1998 Japan Women’s Mid-Amateur Golf Championship | Kagoshima Kuko 36 Country Club Kuko Course | KAGOSHIMA | Keiko Watanabe | |
| 11/26 – 11/29 | |
8th 1998 Japan Senior Open Golf Championship | Ube Country Club Mannenike-East Course | YAMAGUCHI | Graham Marsh |