Edit in JSFiddle

<div class="button">ボタン</div>

body {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}

.button {
    display: inline-block;
    width: 200px;
    height: 54px;
    text-align: center;
    text-decoration: none;
    line-height: 54px;
    outline: none;
    background-color: #1C8BBD;
    border: 2px solid #066590;
    color: #fff;
    line-height: 50px;
    position: relative;
    z-index: 2;
    cursor: pointer;
}
.button,
.button::before,
.button::after {
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
    -webkit-transition: all .5s;
    transition: all .5s;
}
.button::before,
.button::after {
    position: absolute;
    z-index: -1;
    display: block;
    content: '';
    top: 0;
    width: 50%;
    height: 100%;
    background-color: #1C8BBD;
}
.button::before {
    left: 0;
}
.button::after {
    right: 0;
}
.button:hover {
    background-color: #fff;
    border-color: #59b1eb;
    color: #59b1eb;
}
.button:hover::before,
.button:hover::after {
    width: 0;
    background-color: #59b1eb;
}