A glass panel unit includes a first pane of glass, and a second pane of glass facing the first pane of glass with the panes of glass spaced a predetermined interval apart. The glass panel includes a seal disposed between the panes of glass and joined to them in an airtight manner, and an interior space encompassed with the panes of glass and the seal. The glass panel unit includes: a partition wall disposed in the interior space and divides the interior space into a first space as a vacuum space and a second space; an air release vent formed in a first or second pane of glass and communicates with the second space; and a blocking member provided in the air release vent.