A glass panel unit manufacturing method includes a bonding step, a pressure reducing step, and a sealing step. The bonding step includes bonding together a first substrate and a second substrate with a first sealant to create an inner space. The pressure reducing step includes producing a reduced pressure in the inner space through an exhaust port that the first substrate has. The sealing step includes irradiating a second sealant, inserted into the exhaust port, with an infrared ray through a region, where a low emissivity film is nonexistent, of the second substrate.