본문으로 바로가기
<div class="modal fade" id="modal-reg">
    <div class="modal-dialog modal-dialog-centered">
        <div class="modal-content">
            <div class="modal-header"></div>
            <div class="modal-body"></div>
            <div class="modal-footer"></div>
        </div>
    </div>
</div>

class에  modal-dialog-centered 추가