Glass panel unit manufacturing method, building component manufacturing method, glass panel unit manufacturing system, and glass panel unit

A glass panel unit manufacturing method comprising

• an arrangement step of stacking a first substrate, including a glass pane, and a second substrate, including a glass pane, one upon the other with a first sealant in a frame shape interposed between the first substrate and the second substrate;
• a bonding step of bonding together the first substrate and the second substrate with the first sealant to create an inner space surrounded with the first sealant between the first substrate and the second substrate;
• a pressure reducing step of producing a reduced pressure in the inner space through an exhaust port that the first substrate has;
• and
• a sealing step of sealing the exhaust port up while maintaining the reduced pressure in the inner space,
• the sealing step including melting a solid second sealant inserted into the exhaust port by locally heating the second sealant, with the second sealant kept in direct contact with the second substrate, and deforming the second sealant by pressing the second sealant toward the second substrate, to seal the exhaust port up with the second sealant that has expanded in the inner space to bond the second sealant onto both of the first substrate and the second substrate.