To provide a method and a device for performing completion of filling, in which the whole body of free space of an assembly is rapidly filled with a burying material at high density by automatic control.

A free space of the inside of a chamber is filled with a fluid material through an opening provided in the partition wall of the chamber. Such a supply force is used that the fluid material is fed into the chamber. The supply force energizes the fluid material so as to be separated from the opening by allowing independent outward force to be added. The filling degree of a free space of the inside of the chamber is detected. Supply of the fluid material is controlled in correspondence with this detection. The partition wall delimiting the chamber contains a lengthwise part and a shortwise part and the opening is provided in the wall delimiting the lengthwise part. The surface of the fluid material is moved so that the fluid material is directed to the opening along the lengthwise part of the chamber and the fluid material is supplied to the chamber through the opening so as to fill the chamber. Access of the fluid material to the opening in the surface of the fluid material is detected as an index showing that the free space of the inside of the chamber has been filled.