gistfile1.css

/* css checkbox01 */
.checkbox01-input{
  display: none;
}
.checkbox01-parts{
  padding-left: 20px;
  position:relative;
  margin-right: 20px;
}
.checkbox01-parts::before{
  content: "";
  display: block;
  position: absolute;
  top: 0;
  left: 0;
  width: 15px;
  height: 15px;
  border: 1px solid #999;
  border-radius: 4px;
}
.checkbox01-input:checked + .checkbox01-parts{
  color: #009a9a;
}
.checkbox01-input:checked + .checkbox01-parts::after{
  content: "";
  display: block;
  position: absolute;
  top: -5px;
  left: 5px;
  width: 7px;
  height: 14px;
  transform: rotate(40deg);
  border-bottom: 3px solid #009a9a;
  border-right: 3px solid #009a9a;
}

<!-- html -->
<div class="checkbox01">
  <label>
    <input type="checkbox" name="checkbox01[]" class="checkbox01-input">
    <span class="checkbox01-parts">チェックボックス01</span>
  </label>
  <label>
    <input type="checkbox" name="checkbox01[]" class="checkbox01-input">
    <span class="checkbox01-parts">チェックボックス02</span>
  </label>
  <label>
    <input type="checkbox" name="checkbox01[]" class="checkbox01-input">
    <span class="checkbox01-parts">チェックボックス03</span>
  </label>
</div>