Sealants discharged from a syringe are irradiated with activation energy rays from a lamp. Thereby, it takes a predetermined time until the curing of the sealant begins after the irradiation of the activation energy rays. Therefore, the sealant can pass through between the lead wires in the meantime. As a result, a necessary amount of the sealant can enter into the lower side of the lead wire. Thereafter, the sealant begins to be cured and is gradually cured. In consequence, the sealant does not go through between the lead wires to flow into the lower side of the lead wire or flow out into locations other than the sealing location, and can gradually accumulate at the upper side of the lead wire to provide a sufficiently thick sealant.