.header {
    background-image: url('./images/sub_header_pc.jpg');
    height: 270px;
    background-size: cover;
  }
.header__navigation {
    color: #fff !important;
}
  @media screen and (max-width: 768px) {
    .header {
      background-image: url('./images/sub_header_sp.jpg');
      height: 165px !important;
      background-size:100% auto;
    }
  }