以下で、出来るはずですが... <script type="text/javascript"> function fuga(){ sub=window.open('sub.htm'); sub.window.onload = function(){ var tags=sub.document.getElementsByTagName('input'); for(var i=0;i<tags.length;i++){ if(tags[i].name=="btn1"){ tags[i].click(); break; } } } } </script> </head> <body> <input type="button" value="sub" onclick="fuga()"> </body> </html>