javascript appendChild()方法使用错误

Question

// Failed to execute 'appendChild' on 'Node': parameter 1 is not of type 'Node'.

function add(i){
var new_Node = document.createElement("table");
if(0 == i){
var b = document.getElementsByTagName("body")[0];
document.write(new_Node.nodeType);//1
document.write(b.nodeType);//1

         b.appendChild("new_Node");// Failed to execute 'appendChild' on 'Node': parameter 1 is not of type 'Node'.
        }
    
    }