These are the Oricon number one albums of 2004, per the Oricon Albums Chart.
| Indicates best-selling album of 2004 |
| Issue Date | Album | Sales | Artist(s) | |
|---|---|---|---|---|
| January 12 | Wish You the Best | 450,127 | Mai Kuraki | |
| January 19 | 180,186 | |||
| January 26 | Love & Honesty | 296,781 | BoA | |
| February 2 | 145,325 | |||
| February 9 | Jewels | 160,278 | Queen | |
| February 16 | 192,034 | |||
| February 23 | 165,126 | |||
| March 1 | One X One | 325,651 | Chemistry | |
| March 8 | 140,527 | |||
| March 15 | Shining Energy | 117,973 | Joshi Juuni Gakubou | |
| March 22 | Commonplace | 167,248 | Every Little Thing | |
| March 29 | Iro Iro Goromo | 124,621 | Spitz | |
| April 5 | Blue: A Tribute to Yutaka Ozaki | 191,567 | Various Artists | |
| April 12 | bgcolor=#FFFF99 style="text-align: center;" | Utada Hikaru Single Collection Vol. 1 | 1,403,102 | Hikaru Utada |
| April 19 | Shifuku no Oto | 803,422 | Mr. Children | |
| April 26 | bgcolor=#FFFF99 style="text-align: center;" rowspan="4" | Utada Hikaru Single Collection Vol. 1 | 188,428 | Hikaru Utada |
| May 3 | 115,017 | |||
| May 10 | 110,126 | |||
| May 17 | 73,385 | |||
| May 24 | Under My Skin | 286,894 | Avril Lavigne | |
| May 31 | 122,461 | |||
| June 7 | Aratanaru Kōshinryō o Motomete | 137,131 | Naotaro Moriyama | |
| June 14 | 86,274 | |||
| June 21 | 57,251 | |||
| June 28 | 54,107 | Misia | ||
| July 5 | TMG I | 90,281 | TMG | |
| July 12 | Do You Know? | 141,377 | Nobodyknows+ | |
| July 19 | 68,146 | |||
| July 26 | Trunk | 232,519 | HY | |
| August 2 | Iza, Now! | 115,241 | Arashi | |
| August 9 | Porno Graffitti Best Blue's | 400,318 | Porno Graffitti | |
| August 16 | 145,217 | |||
| August 23 | Explorer | 157,648 | Noriyuki Makihara | |
| August 30 | [sí:] | 161,058 | Tsuyoshi Domoto | |
| September 6 | Yggdrasil | 315,065 | Bump of Chicken | |
| September 13 | TOK10 | 97,156 | Tokio | |
| September 20 | Exodus | 523,761 | Utada | |
| September 27 | 1: One | 217,648 | Yuzu | |
| October 4 | Peace of Mind | 220,127 | Koshi Inaba | |
| October 11 | Heart of Gold: Street Future Opera Beat Pops | 247,852 | Exile | |
| October 18 | 86,251 | |||
| October 25 | Fullmetal Alchemist: Complete Best | 108,612 | Various Artists | |
| November 1 | Sol-fa | 300,468 | Asian Kung-Fu Generation | |
| November 8 | 99,407 | |||
| November 15 | 173,145 | Britney Spears | ||
| November 22 | 126,532 | Arashi | ||
| November 29 | Love Jam | 224,381 | Ai Otsuka | |
| December 6 | Sentimentalovers | 687,516 | Ken Hirai | |
| December 13 | MusiQ | 872,716 | Orange Range | |
| December 20 | 401,231 | |||
| December 27 | My Story | 574,321 | Ayumi Hamasaki | |