document.write("<p><input type=\"button\" value=\"追加\" onclick=\"addRowTable()\" />（入力欄を追加します）</p>");
document.write("<table id=\"addition\" border=\"1\">");
document.write("<tr>");
document.write("<th colspan=\"2\">行の追加生成</th>");
document.write("</tr>");
document.write("<tr>");
document.write("<td>1</td>");
document.write("<td><input type=\"text\" name=\"input1\" size=\"40\" value=\"\" /></td>");
document.write("</tr>");
document.write("</table>");

function addRowTable() {
var tbl = document.getElementById('addition');
var lastRow = tbl.rows.length;
var increment = lastRow;
var row = tbl.insertRow(lastRow);
var cellLeft = row.insertCell(0);
var textNode = document.createTextNode(increment);
var cellRight = row.insertCell(1);
var control = document.createElement('input');
control.setAttribute('type', 'text');
control.setAttribute('name', 'input' + increment);
control.setAttribute('id', 'input' + increment);
control.setAttribute('size', '40');
cellLeft.appendChild(textNode);
cellRight.appendChild(control);
}