window.onload = function(){
setInterval("swapPhoto()", 6000);
}
// 画像を交互に入れ替えるための関数

function swapPhoto(){
	if(document.getElementById('visual_1').style.display == "block"){
        document.getElementById('visual_1').style.display = "none";
        document.getElementById('visual_2').style.display = "block";
        document.getElementById('visual_3').style.display = "none";
        document.getElementById('visual_4').style.display = "none";
    }else if(document.getElementById('visual_2').style.display == "block"){
        document.getElementById('visual_1').style.display = "none";
        document.getElementById('visual_2').style.display = "none";
        document.getElementById('visual_3').style.display = "block";
        document.getElementById('visual_4').style.display = "none";
	}else if(document.getElementById('visual_3').style.display == "block"){
        document.getElementById('visual_1').style.display = "none";
        document.getElementById('visual_2').style.display = "none";
        document.getElementById('visual_3').style.display = "none";
        document.getElementById('visual_4').style.display = "block";
	}else if(document.getElementById('visual_4').style.display == "block"){
        document.getElementById('visual_1').style.display = "block";
        document.getElementById('visual_2').style.display = "none";
        document.getElementById('visual_3').style.display = "none";
        document.getElementById('visual_4').style.display = "none";
    }
}