The glass panel unit is a predetermined part separated from a completed assembly obtained by subjecting a temporary assembly to a predetermined process. In the temporary assembly, the inside space (500) enclosed by the first and second glass substrates and the frame is divided into the first space and the second space with the partition and the gas adsorbent is inside the first space. The predetermined process includes: converting the first space into the evacuated space by evacuating the first space through the gas passage, the second space, and the outlet; and changing a shape of the partition to close the gas passage to form the seal enclosing the evacuated space. The predetermined part includes: a first and second glass panels being parts of the first and second glass substrates; the seal; the evacuated space; and the gas adsorbent.