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 1985.
| Issue date | Song | Artist(s) | Ref. |
|---|---|---|---|
| January 7 | "" | Kyōko Koizumi | [1] |
| January 14 | |||
| January 21 | "" | Kōji Kikkawa | |
| January 28 | |||
| February 4 | |||
| February 11 | "" | Seiko Matsuda | |
| February 18 | |||
| February 25 | "Yoisho!" (ヨイショッ | ) | Masahiko Kondō |
| March 4 | "" | The Alfee | |
| March 11 | "" | Momoko Kikuchi | |
| March 18 | "Mi Amore (Meu amor é...)" | Akina Nakamori | |
| March 25 | |||
| April 1 | "" | The Checkers | |
| April 8 | |||
| April 15 | |||
| April 22 | "" | Kyōko Koizumi | |
| April 29 | |||
| May 6 | "" | Kōji Kikkawa | |
| May 13 | "Akaitori Nigeta" | Akina Nakamori | |
| May 20 | "" | Seiko Matsuda | |
| May 27 | "" | Momoko Kikuchi | |
| June 3 | |||
| June 10 | "" | Yumi Matsutoya, Kazumasa Oda, | |
| June 17 | |||
| June 24 | "" | Naoko Kawai | |
| July 1 | "Sand Beige (Sabaku e)" | Akina Nakamori | |
| July 8 | "" | Seiko Matsuda | |
| July 15 | "" | The Checkers | |
| July 22 | |||
| July 29 | |||
| August 5 | "" | Kyōko Koizumi | |
| August 12 | "" | Anzen Chitai | |
| August 19 | |||
| August 26 | "" | Toshihiko Tahara | |
| September 2 | "Kanashimi ni Sayonara" | Anzen Chitai | |
| September 9 | |||
| September 16 | "" | Sonoko Kawai | |
| September 23 | |||
| September 30 | "" | The Checkers | |
| October 7 | "" | Momoko Kikuchi | |
| October 14 | |||
| October 21 | "Solitude" | Akina Nakamori | |
| October 28 | "" | Akiko Kobayashi | |
| November 4 | |||
| November 11 | "" | The Checkers | |
| November 18 | "Koi ni Ochite: Fall in Love" | Akiko Kobayashi | |
| November 25 | |||
| December 2 | "" | Kyōko Koizumi | |
| December 9 | "Koi ni Ochite: Fall in Love" | Akiko Kobayashi | |
| December 16 | |||
| December 23 | "Kamen Butōkai" | Shonentai | |
| December 30 | "Koi ni Ochite: Fall in Love" | Akiko Kobayashi |