Thank you very much! All of you! I did not even realize that there exists so many tools for that. I tried to use all suggested apps but most of them failed. More precisely, I failed because, as I suppose, I did not use it properly. Anyway, finally I used DBeaver and DbSchema (Free edition). Both works as expected and were able to prepare ER Diagrams for PostgreSQL schema with 500+ tables. It looks astonish, really. A small example, generated by DbSchema, can be seen below. 🙂
Thank a lot again.