The glass panel unit 10 includes: a first glass panel 20; a second glass panel 30; a seal 40; an evacuated space 50; and a gas adsorbent 60. The seal 40 with a frame shape hermetically bonds the first glass panel 20 and the second glass panel 30 to each other. The gas adsorbent 60 is placed in the evacuated space 50. The gas adsorbent 60 includes a getter. The gas adsorbent 60 is visible through at least one of the first glass panel 20 and the second glass panel 30. The gas adsorbent 60 has properties of changing its color when adsorbing gas.