Custom posts loading problem

Hi
I am new to WordPress, I have developed a theme from scratch. I have created a custom post type “portfolio” and I want to load the added post into my page using below codes.

<?php
    $args = array('post_type'=>'Portfolio');
    $query = new WP_Query($args);

    if($query->have_posts()) : while($query->have_posts()) : $query->the_post();?>

        <h1><?php the_title(); ?></h1>
        <p> <?php the_content()?></p>

    <?php endwhile; endif; wp_reset_postdata(); ?>

But just the first post is loaded. I think the loop dose not work. what do you think? what is the problem?
Thanks.