listing_by_category.php

<?php

// Category args.
$args = array(
	'type'                     => 'post',
	'child_of'                 => 0,
	'parent'                   => '',
	'orderby'                  => 'name',
	'order'                    => 'ASC',
	'hide_empty'               => 1,
	'hierarchical'             => 1,
	'exclude'                  => '',
	'include'                  => '',
	'number'                   => '',
	'taxonomy'                 => 'category',
	'pad_counts'               => false 
); 

// Get category list.
$categories = get_categories( $args );

// Listing all category.
foreach ($categories as $category): ?>

	<div class="category-item">
		<div class="category-item__title">
			<?php echo $category->name; ?>
		</div>

		<div class="category-item__post-list">
		<?php 
			// Query args.
			$query_args = array(
				'cat' 				=> $category->term_id,
				'posts_per_page' 		=> -1,
				'orderby'                  	=> 'date',
				'order'                    	=> 'DESC',
			);

			$query = new WP_Query( $query_args );

			// Start the loop.
			while ( $query->have_posts() ) : $query->the_post();
			
				echo get_the_title().'<br/>';
				
			// End the loop.
			endwhile; 
		?>
		</div>
	</div>

	<?php 
endforeach; 	

?>