To prevent solder granulates from being crushed and improve the accuracy of the packing of a fixed amount of soldering paste when the soldering paste is introduced, by using two nozzles, i.e., a large one and a small one, in combination, which are so constructed that each nozzle formed into a flexible tube shape is choked by a side pressure.

A nozzle opening/closing apparatus 5 is constructed by disposing reciprocatively a pair of press bodies 5a, 5a on both sides of a nozzle formed into a rubber or a plastic tube shape and made of a flexible material. Each press body has a width broader than a diameter of the tube, and a top end thereof is sharp triangularly in a cross section. The respective press bodies 5a, 5a are movably fitted into guide cylinders 5b, 5b fixed to a frame 1a and are connected to piston rods 5d, 5d of air cylinder units 5c, 5c. Two of the nozzle opening/closing apparatus 5 having such a construction, i.e., a large one and a small one, are provided in parallel with each other, and the most part of soldering paste is introduced by a large nozzle, while a minute amount thereof is introduced by a small nozzle, whereby a fixed amount of soldering paste can be introduced accurately without crushing solder granulates in the paste.