A slot nozzle assembly for extruding a foamable melted material in a wide band including a plurality of foamable melted material passages, lateral distribution flow routes communicating with the plurality of foamable melted material passages, a restriction member disposed inside the lateral distribution flow routes, a slot for discharging foamable melted material, and a converging portion which communicates with the lateral distribution flow routes and the slot, and whose cross-section area gradually becomes smaller toward the slot.