EXCLUSIVE

Stan Lee just sued his ex-business manager, alleging the guy swindled him out of more than $1.4 million ... and sources tell us Stan wants $20 million to make him pay.

Stan's lawyer, Jonathan Freund, filed legal docs claiming Jerardo Olivarez set him up in disastrous business deals but more importantly ... Stan's pointing the finger at him as the guy who bought an $850k condo without Stan's permission and also may have forged a $300k check.

In docs, obtained by TMZ, Stan also claims Olivarez had a nurse inject Stan with a syringe and extract his blood to sell it in Las Vegas as a collectible. What's more ... Stan claims Olivarez got him into crappy deals to sell his name and likeness. Stan claims that's caused him to get sued for millions of dollars.