<input id="cb_9" name="cb1[]" value="9" onclick="showSubMenu(this.value);" checked="checked" type="checkbox">
<div id="div_9" class="cb_box_show">
   <input name="cb2[]" value="9/20" type="checkbox" checked="checked">
   <input name="cb2[]" value="9/16" type="checkbox">
   <input name="cb2[]" value="9/17" type="checkbox">
</div>

<input id="cb_10" name="cb1[]" value="10" onclick="showSubMenu(this.value);" checked="checked" type="checkbox">
<div id="div_10" class="cb_box_show">
   <input name="cb2[]" value="10/20" type="checkbox" checked="checked">
   <input name="cb2[]" value="10/16" type="checkbox">
   <input name="cb2[]" value="10/17" type="checkbox">
</div>

<input id="cb_9" name="cb1[]" value="9" onclick="showSubMenu(this.value);" checked="checked" type="checkbox">

<div id="div_9" class="cb_box_show">

document.getElementById('div_9').getElementsByTagName('input')

(function () {
	var a = document.getElementsByTagName('input');
	for (var i = 0; i < a.length; i++) {
		if (a[i].name == 'cb2[]' && a[i].type == 'checkbox') {
			a[i].checked = false;
		}
	}
})();