| February | |
| 04 | 22nd single "READY STEADY GO" release *Oricon chart first appearance No.1 |
| March | |
| 03 | 23rd single "Hitomi No Jyunin" release *Oricon chart first appearance No.1 |
| 31 | 9th album "SMILE" release *Oricon chart first appearance No.2 |
| April | |
| 21 | Album "DUNE-10th Anniversary Edition" release |
| May | |
| 08 | Special live entitled "SMILE TOUR 2004 Zenyasai" at Sony Music Fes.2004 （Kokuritsu Yoyogi Kyogijo Daiichi Taiikukan） (Invited 10,000 people from the people who purchase the album "SMILE") |
| 11 | "SMILE TOUR 2004" starts from Yokohama Arena |
| 12 | Yokohama Arena |
| 15 | Nagoya Rainbow Hall |
| 16 | Nagoya Rainbow Hall |
| 22 | Sendai Shimin Taiikukan |
| 23 | Sendai Shimin Taiikukan |
| 29 | Sapporo Kitaeeru |
| 30 | Sapporo Kitaeeru |
| June | |
| 02 | 24th single "Jiyuu eno shoutai" release *Oricon chart first appearance No.1 (Commercial film song for Daihatsu "MOVE CUSTOM") |
| 09 | Osakajo Hall |
| 10 | Osakajo Hall |
| 12 | Osakajo Hall（Additional show） |
| 13 | Osakajo Hall（Additional show） |
| 18 | Marin Messe Fukuoka |
| 19 | Marin Messe Fukuoka |
| 23 | Kokuritsu Yoyogi Kyogijo Daiichi Taiikukan |
| 24 | Kokuritsu Yoyogi Kyogijo Daiichi Taiikukan |
| 26 | Kokuritsu Yoyogi Kyogijo Daiichi Taiikukan（Additional show） |
| 27 | Kokuritsu Yoyogi Kyogijo Daiichi Taiikukan（Additional show） (7 venues, 18 performances / 250,000 people) |
| 29 | Album "SMILE" release in USA |
| 30 | Official band score "SMILE" from Sony Magazines release |
| July | |
| 24 | Appear at event "THE ROCK ODYSSEY 2004" (Osaka Dome) |
| 25 | Appear at event "THE ROCK ODYSSEY 2004" (International Stadium Yokohama) |
| 31 | Hold "L'Arc-en-Ciel Live in USA" in Baltimore, MD, USA (1st Mariner Arena) as part of event "OTAKON 2004" |
| September | |
| 02 | Poster Book "SMILE TOUR 2004" release from PIA corporation / Only available on mail order (No OTC sales) |
| 30 | Live Photo Book "SMILE TOUR 2004" release from PIA corporation |
| October | |
| 01 | Start recording |
| December | |
| 08 | LIVE DVD "LIVE IN USA -at 1st Mariner Arena July 31, 2004" release |
| 19 | Holds Secret Gig at event "FULLMETAL ALCHEMIST FESTIVAL" (Osaka-Jo Hall) |
| 24 | Appears on "MUSIC STATION SUPER LIVE 2004" (TV Asahi Network) |
| 25 | Holds Secret Gig at event "Tencha San -DANGER III-" (Nippon Budokan) (Appears also as P'UNK-EN-CIEL) |
| 26 | Holds Secret Gig at event "FULLMETAL ALCHEMIST FESTIVAL" (Kokuritsu Yoyogi Kyogijo Daiichi Taiikukan) |
