EXCLUSIVE

imageThe kid who plays the young version of "The Big Bang Theory" character Sheldon Cooper is getting a big boost to his bank account ... thanks to the huge success of the CBS spin-off.

According to Iain Armitage's "Young Sheldon" contract -- obtained by TMZ -- the star of the show got $30,000 for every episode in Season 1 ... which ended up being 22 strong after a stellar ratings debut scored it a full-season order.

Do the math, and that's $660k for Young Sheldon.

It gets better, though -- the show's been renewed for Season 2, which premieres in September, and will likely be another 22 eps. According to his contract, he'll get a pay bump to $31,200 per ep. for the second season ... which comes out to more than a $26k raise.

That's roughly $1.35 MILLION for Iain for 2 seasons of TV work.

And if season 3 happens, it's the same deal for Sheldon -- more eps. for more money ... $32,448 a pop.

Sure beats a paper route.

Read more from our friends at TMZ