A sealant forming nozzle is disposed to seal an object that a sectional shape in a first plane is a stair shape. The sealant forming nozzle includes a shaping section and a guide section. The shaping section includes a shaping surface orthogonal to the first plane, and a sealant output hole to supply a sealant to a space surrounded by the object and the shaping surface. The guide section has a guide surface. The guide surface is orthogonal to the first plane and formed to have a line contact with a corner section of an upper step of the stair shape.