function RandomImage(){
img = new Array();

//以下イメージ名指定（img[0] = "http://www.onealjapan.com/yyyy/XXXXXXXX.jpg";）

img[0] = "http://www.onealjapan.com/top/main01.jpg"
img[1] = "http://www.onealjapan.com/top/main07.jpg";
img[2] = "http://www.onealjapan.com/top/main08.jpg";
img[3] = "http://www.onealjapan.com/top/main09.jpg";
// img[4] = "http://www.onealjapan.com/top/main05.jpg";
// img[5] = "http://www.onealjapan.com/top/main06.jpg";

//ランダムに切り替え

n = Math.floor(Math.random()*img.length);
document.getElementById("main_image").setAttribute("src",img[n]);
}