The following is a list of Oricon number-one singles of 2004.
| Issue date | Song | Artist(s) | Ref. |
|---|---|---|---|
| January 5 | No chart data available | [1] | |
| January 12 | "Sekai ni Hitotsu Dake no Hana" | SMAP | |
| January 19 | "Star Gazer" | Spitz | |
| January 26 | "Toki no Shizuku" | Glay | |
| February 2 | "READY STEADY GO" | L'arc-en-Ciel | |
| February 9 | "One Day, One Dream" | Tackey & Tsubasa | |
| February 16 | "PIKA☆☆NCHI DOUBLE" | Arashi | |
| February 23 | "Michishirube ~a road home~" | Orange Range | |
| March 1 | "Hitomi no Juunin" | L'arc-en-Ciel | |
| March 8 | "Wonderful Life" | &G | |
| March 15 | "Subete ga Boku no Chikara ni Naru!" | Kuzu | |
| March 22 | "Arigatou no Uta" | V6 | |
| March 29 | "Moments" | Ayumi Hamasaki | |
| April 5 | |||
| April 12 | "Aja" | Southern All Stars | |
| April 19 | "Dareka no Negai ga Kanau Koro" | Hikaru Utada | |
| April 26 | |||
| May 3 | "Banzai" | B'z | |
| May 10 | "Kibou: Yell" | NEWS | |
| May 17 | "Tenshi no Wakemae" | Glay | |
| May 24 | "Sign" | Mr. Children | |
| May 31 | "Jiyuu e no Shoutai" | L'arc-en-Ciel | |
| June 7 | "Waver" | Domoto Tsuyoshi | |
| June 14 | "Locolotion" | Orange Range | |
| June 21 | |||
| June 28 | "Real World" | Exile | |
| July 5 | "Only Lonely Glory" | Bump of Chicken | |
| July 12 | "Wonderland" | Koshi Inaba | |
| July 19 | "Kimi Koso Star da" | Southern All Stars | |
| July 26 | "Inspire" | Ayumi Hamasaki | |
| August 2 | "Blue Jean" | Glay | |
| August 9 | "Akaku Moyuru Taiyou" | NEWS | |
| August 16 | "Hitomi no Naka no Galaxy" | Arashi | |
| August 23 | "Chest" | Orange Range | |
| August 30 | "Arigato" | B'z | |
| September 6 | "Mickey" | Gorie with Jasmine & Joann | |
| September 13 | |||
| September 20 | "Naniwa Iroha Bushi" | Kanjani8 | |
| September 27 | "Carols" | Ayumi Hamasaki | |
| October 4 | "Omoi ga Kasanaru Sono Mae ni..." | Ken Hirai | |
| October 11 | |||
| October 18 | "Hana" | Orange Range | |
| October 25 | |||
| November 1 | |||
| November 8 | "108.681" | TM Revolution | |
| November 15 | "Hana" | Orange Range | |
| November 22 | "Ai to Yokubou no Hibi" | Southern All Stars | |
| November 29 | "Naitari Shinaide / Red x Bue" | Masaharu Fukuyama | |
| December 6 | "White Road" | Glay | |
| December 13 | "Koibumi / Good Night" | Every Little Thing | |
| December 20 | "Anniversary" | KinKi Kids | |
| December 27 | |||