The 48-year-old actor earned an estimated USD 75 million from June 2012 to June 2013, reports femalefirst.co.uk.
Downey Jr. has beaten actors Channing Tatum and Hugh Jackman in the run.
Tatum, who is at the second position, made USD 60 million and Jackman, third on the list, made $55 million in the year.
Actor Mark Wahlberg, 42, who earned USD 52 million, is listed at the fouth position.
Others in the top 10 included actors Dwayne Johnson, Leonardo DiCaprio, Adam Sandler, Tom Cruise, Denzel Washington and Liam Neeson.
Birthday special: 14 Bollywood actors who made it big on TV
Photos: Vaani Kapoor, Poonam Pandey, Sana Khan at fashion event
Photos: Rishi Kapoor, wife Neetu, daughter Riddhima at book launch
Photos: Sunny Leone, Shraddha Kapoor, Shriya Saran at Mumbai airport
How Angelic! 10 stunning pics of birthday girl Angelique Kerber