Ok, i found a solution.
If you want Kindle to manage justification you have to convert e-book to html, edit it and make sure that paragraphs that has to be justified are <p class="calibre4"> </p>.
Maybe not olny 'calibre4' works ok, but i dont know where to find specific class properities that Calibre uses when converting.
When html is prepared you can convert it to mobi (Option 'Look and feel>Text justification' set to 'Original') and "Justification" option in Kindle 3 menu (which is not visible by default) will work perfectly.