These are the Oricon number one albums of 1998, per the Oricon Albums Chart.
| Indicates best-selling album of 1998 |
| Issue Date | Album | Artist(s) | |
|---|---|---|---|
| January 12 | Storytelling | Tomomi Kahala | |
| January 19 | Works: The Best of TRF | TRF | |
| January 26 | |||
| February 2 | Triple Joker | T.M. Revolution | |
| February 9 | 181920 | Namie Amuro | |
| February 16 | |||
| February 23 | Super Heroes | V6 | |
| March 2 | Missing Place | Favorite Blue | |
| March 9 | Heart | L'Arc-en-Ciel | |
| March 16 | Punch Drunkard | The Yellow Monkey | |
| March 23 | The Boøwy | Boøwy | |
| March 30 | Deen Singles +1 | Deen | |
| April 6 | Fake Fur | Spitz | |
| April 13 | Love again | Globe | |
| April 20 | Jet-CD | Puffy | |
| April 27 | Time to Destination | Every Little Thing | |
| May 4 | |||
| May 11 | Rise | Speed | |
| May 18 | |||
| May 25 | Kumuiuta | Cocco | |
| June 1 | bgcolor=#FFFF99 style="text-align: center;" rowspan="4" | B'z The Best "Pleasure" | B'z |
| June 8 | |||
| June 15 | |||
| June 22 | |||
| June 29 | Smap 012 Viva Amigos | SMAP | |
| July 6 | Umi no Yeah!! | Southern All Stars | |
| July 13 | |||
| July 20 | Crimson | Nanase Aikawa | |
| July 27 | Mother Father Brother Sister | Misia | |
| August 3 | Shine | Luna Sea | |
| August 10 | Pure Soul | Glay | |
| August 17 | |||
| August 24 | B Album | KinKi Kids | |
| August 31 | Mahō no Te | Tōko Furuuchi | |
| September 7 | Cozy | Tatsuro Yamashita | |
| September 14 | New Adventure | My Little Lover | |
| September 21 | Mother Earth | Maki Ohguro | |
| September 28 | B'z The Best "Treasure" | B'z | |
| October 5 | |||
| October 12 | |||
| October 19 | Nagai Aida: Kiroro no Mori | Kiroro | |
| October 26 | Samurai | Tsuyoshi Nagabuchi | |
| November 2 | Sakura | Southern All Stars | |
| November 9 | |||
| November 16 | Neue Muzik | Yumi Matsutoya | |
| November 23 | |||
| November 30 | The #1's | Mariah Carey | |
| December 7 | |||
| December 14 | Maximum Groove | MAX | |
| December 21 | Relation | Globe | |
| December 28 | Moment | Speed | |