There are many design and constructed examples of the steel-concrete tied arch bridge in EU countries where the tension stiffening effect of concrete is taken into account. In designing of steel tied arch bridge having RC slab, however, the conservative design method, that is non-composite design, has been accepted in Japan. But in near future in Japan too, it seems that the composite design for tied arch bridge will be adopted. However, the adequate concrete placing sequence of the concrete slabs in composite tied arch bridge is not clarified perfectly. This paper reports the result concerning the optimum concrete placing method in compcsite tied arch bridge.