Thank you for the answer.
I added below in my enfold-child theme’s functions.php.
But the blog subject is still same. “blog-latest” (블로그-최근뉴스)

add_filter(‘avf_title_args’, ‘fix_single_post_title’, 10, 2);
function fix_single_post_title($args,$id)
{
if ( $args[‘title’] == ‘Blog – Latest News’ )
{
$args[‘title’] = get_the_title($id);
$args[‘link’] = get_permalink($id);
$args[‘heading’] = ‘h1’;
$title = __(‘Blog – Latest News’, ‘avia_framework’); //default blog title
}

return $args;
}