Casey Anthony's Lawyer Jose Baez -- I QUIT!

Casey Anthony is on her own ... 'cause the attorney who got her off murder charges has decided to REMOVE HIMSELF from Anthony's legal team.

Anthony first hooked up with Jose Baez while she was in jail -- and heard other inmates raving about his work.

It's unclear why Baez tendered his resignation ... though it's rumored the two were having a falling out after Anthony's private video diaries surfaced online.