These are the Oricon number one albums of 2004, per the Oricon Albums Chart.
| † | Indicates best-selling album of 2004 |
| Issue Date [1] | 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 [2] | 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 [3] | Blue: A Tribute to Yutaka Ozaki | 191,567 | Various Artists |
| April 12 | Utada Hikaru Single Collection Vol. 1 † | 1,403,102 | Hikaru Utada |
| April 19 | Shifuku no Oto | 803,422 | Mr. Children |
| April 26 | 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 [4] | 86,274 | ||
| June 21 [5] | 57,251 | ||
| June 28 [6] | Misia Love & Ballads: The Best Ballade Collection | 54,107 | Misia |
| July 5 [7] | TMG I | 90,281 | TMG |
| July 12 [8] | Do You Know? | 141,377 | Nobodyknows+ |
| July 19 [9] | 68,146 | ||
| July 26 [10] | Trunk | 232,519 | HY |
| August 2 | Iza, Now! | 115,241 | Arashi |
| August 9 [11] | Porno Graffitti Best Blue's | 400,318 | Porno Graffitti |
| August 16 [12] | 145,217 | ||
| August 23 [13] | Explorer | 157,648 | Noriyuki Makihara |
| August 30 [14] | [sí:] | 161,058 | Tsuyoshi Domoto |
| September 6 [15] | Yggdrasil | 315,065 | Bump of Chicken |
| September 13 [16] | TOK10 | 97,156 | Tokio |
| September 20 [17] | Exodus | 523,761 | Utada |
| September 27 [18] | 1: One | 217,648 | Yuzu |
| October 4 [19] | Peace of Mind | 220,127 | Koshi Inaba |
| October 11 [20] | Heart of Gold: Street Future Opera Beat Pops | 247,852 | Exile |
| October 18 [21] | 86,251 | ||
| October 25 [22] | Fullmetal Alchemist: Complete Best | 108,612 | Various Artists |
| November 1 [23] | Sol-fa | 300,468 | Asian Kung-Fu Generation |
| November 8 [24] | 99,407 | ||
| November 15 [25] | Greatest Hits: My Prerogative | 173,145 | Britney Spears |
| November 22 [26] | Arashi 5x5: The Best Selection of 2002–2004 | 126,532 | Arashi |
| November 29 [27] | Love Jam | 224,381 | Ai Otsuka |
| December 6 [28] | Sentimentalovers | 687,516 | Ken Hirai |
| December 13 [29] | MusiQ | 872,716 | Orange Range |
| December 20 [30] | 401,231 | ||
| December 27 | My Story | 574,321 | Ayumi Hamasaki |