The actor, 39 – who stars in new film Hancock - topped the poll, beating Johnny Depp, 45, into second with £36million.
Eddie Murphy, 47, and Mike Myers, 45, came joint third with £27.5million each.
And Leonardo DiCaprio, 33, rounded off the top 5 by raking in £22.5million in the last 12 months.
Cameron Diaz, 35, who earned £25million last year, topped the female poll.
Top 5 Best paid actors:
1. Will Smith - £40million
2. Johnny Depp - £36million
3. Eddie Murphy and Mike Myers - £27.5million
5. Leonardo DiCaprio - £22.5million
Top 5 Best paid actresses:
1. Cameron Diaz - £25million
2. Keira Knightley - £16million
3. Jennifer Aniston - £13.5million
4. Reese Witherspoon - £12.5million
5. Gwyneth Paltrow - £12.5million