#header #searchform select,
#header .search .input_search {
    float: right;
}

{#
This file is part of EC-CUBE

Copyright(c) 2000-2015 LOCKON CO.,LTD. All Rights Reserved.

http://www.lockon.co.jp/

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
#}
<div class="drawer_block pc header_bottom_area">
    <div id="search" class="search">
        <form method="get" id="searchform" action="{{ path('product_list') }}">
            <div class="search_inner">
                <div class="input_search clearfix">
                    {{ form_widget(form.name, {'attr': { 'placeholder' : "キーワードを入力" }} ) }}
                    <button type="submit" class="bt_search"><svg class="cb cb-search"><use xlink:href="#cb-search" /></svg></button>
                </div>
                {{ form_widget(form.category_id) }} {# ==== ここに移動 ==== #}
            </div>
            <div class="extra-form">
                {% for f in form.getIterator %}
                    {% if f.vars.name matches '[^plg*]' %}
                        {{ form_label(f) }}
                        {{ form_widget(f) }}
                        {{ form_errors(f) }}
                    {% endif %}
                {% endfor %}
            </div>
        </form>
    </div>
</div>

#header #searchform select,
#header .search .input_search {
    float: right;
}