These are the Oricon number one albums of 2005, per the Oricon Albums Chart.
| Issue Date | Album | Sales | Artist(s) |
|---|---|---|---|
| January 3 | KinKi Single Selection II | 356,117 | KinKi Kids |
| January 17 | Perfect Best | 970,126 | Exile |
| January 24 | Souvenir | 175,815 | Spitz |
| January 31 | Ballad Best Singles: White Road | 244,166 | Glay |
| February 7 | Hot Chemistry | 104,856 | Chemistry |
| February 14 | Best of Soul | 489,067 | BoA |
| February 21 | Early Times | 201,354 | Love Psychedelico |
| February 28 | 90,341 | ||
| March 7 | Joy | 135,624 | Yuki |
| March 14 | Yume no Naka no Massugu na Michi | 254,756 | Aiko |
| March 21 | Music | 231,521 | Mika Nakashima |
| March 28 | 88,024 | ||
| April 4 | Def Tech | 75,346 | Def Tech |
| April 11 | 82,459 | ||
| April 18 | The Circle | 345,041 | B'z |
| April 25 | E: Complete A side Singles | 98,362 | Zone |
| May 2 | Thumpx | 215,219 | Porno Graffitti |
| May 9 | Touch | 164,016 | NEWS |
| May 16 | Def Tech | 99,236 | Def Tech |
| May 23 | Make Progress | 92,154 | Nami Tamaki |
| May 30 | Def Tech | 62,532 | Def Tech |
| June 6 | Don't Believe the Truth | 95,026 | Oasis |
| June 13 | Ageha | 76,514 | W-inds |
| June 20 | Home [1997~2000] | 320,541 | Yuzu |
| June 27 | Sou Kana | 171,026 | Kazumasa Oda |
| July 4 | Awake | 225,137 | L'Arc-en-Ciel |
| July 11 | Ketsunopolis 4 | 947,826 | Ketsumeishi |
| July 18 | 308,057 | ||
| July 25 | 220,916 | ||
| August 1 | Kūsō Clip | 146,180 | Sukima Switch |
| August 8 | Sample Bang! | 285,236 | SMAP |
| August 15 | One | 121,187 | Arashi |
| August 22 | DiscO-Zone | 44,440 | O-Zone |
| August 29 | 66,761 | ||
| September 5 | Beat Space Nine | 140,823 | M-Flo |
| September 12 | Good Job! | 350,054 | Rip Slyme |
| September 19 | Rio de Emocion | 93,258 | Dragon Ash |
| September 26 | Have a Nice Day | 123,410 | Bon Jovi |
| October 3 | I♥U | 686,688 | Mr. Children |
| October 10 | Best ~First Things~ | 195,290 | Kumi Koda |
| October 17 | Killer Street | 633,490 | Southern All Stars |
| October 24 | Иatural | 510,473 | Orange Range |
| October 31 | 165,752 | ||
| November 7 | #1's | 154,859 | Destiny's Child |
| November 14 | Kidō Senshi Gundam SEED Destiny Complete Best | 194,233 | Various Artists |
| November 21 | Japana-rhythm | 178,919 | Bennie K |
| November 28 | H Album: Hand | 245,681 | KinKi Kids |
| December 5 | 10th Anniversary Complete Single Collection '95-'05 "Utabaka" | 927,989 | Ken Hirai |
| December 12 | B'z The Best "Pleasure II" | 761,940 | B'z |
| December 19 | Best | 480,097 | Mika Nakashima |
| December 26 | Love Cook | 334,812 | Ai Otsuka |
