The highest-selling singles in Japan are ranked in the Oricon Singles Chart, which is published by Oricon Style magazine. The data are compiled by Oricon based on each singles' physical sales. This list includes the singles that reached the number one place on that chart in 1984.
| Issue date | Song | Artist(s) | Ref. |
|---|---|---|---|
| January 2 | "" | Warabe | [1] |
| January 9 | |||
| January 16 | |||
| January 23 | |||
| January 30 | |||
| February 6 | |||
| February 13 | "" | Seiko Matsuda | |
| February 20 | |||
| February 27 | |||
| March 5 | |||
| March 12 | "" | Masahiko Kondō | |
| March 19 | "" | Anzen Chitai | |
| March 26 | |||
| April 2 | "" | Kyōko Koizumi | |
| April 9 | "" | Shibugakitai | |
| April 16 | |||
| April 23 | "Southern Wind" | Akina Nakamori | |
| April 30 | |||
| May 7 | |||
| May 14 | "" | The Checkers | |
| May 21 | "" | Seiko Matsuda | |
| May 28 | |||
| June 4 | "" | Toshihiko Tahara | |
| June 11 | |||
| June 18 | "" | Masahiko Kondō | |
| June 25 | |||
| July 2 | "" | Kyōko Koizumi | |
| July 9 | |||
| July 16 | "" | Asami Kobayashi | |
| July 23 | |||
| July 30 | |||
| August 6 | "Jukkai (1984)" | Akina Nakamori | |
| August 13 | "" | Seiko Matsuda | |
| August 20 | "" | Toshihiko Tahara | |
| August 27 | "Jukkai (1984)" | Akina Nakamori | |
| September 3 | "" | The Checkers | |
| September 10 | |||
| September 17 | |||
| September 24 | "Eien ni Himitsu sa" (永遠に秘密さ) | Masahiko Kondō | |
| October 1 | "" | Kyōko Koizumi | |
| October 8 | |||
| October 15 | |||
| October 22 | "" | Tomoyo Harada | |
| October 29 | "" | The Alfee | |
| November 5 | "" | Hiroko Yakushimaru | |
| November 12 | "" | Seiko Matsuda | |
| November 19 | |||
| November 26 | "Kazari ja Nai no yo Namida wa" | Akina Nakamori | |
| December 3 | "" | The Checkers | |
| December 10 | |||
| December 17 | |||
| December 24 | |||
| December 31 | "" | Kyōko Koizumi |