Glass panel unit manufacturing method

A glass panel unit manufacturing method, comprising:

• a bonding step of bonding a first substrate and a second substrate together with a bonding material provided between the first substrate and the second substrate and having a frame shape to form an internal space, the first substrate including a glass panel and having an evacuation port, the second substrate including a glass panel, the internal space being surrounded by the bonding material between the first substrate and the second substrate;
• an insertion step of inserting a sealing material into the evacuation port of the first substrate;
• an evacuation step of evacuating the internal space through an exhaust passage by detachably connecting the exhaust passage to the evacuation port;
• and
• a sealing step of:
• deforming the sealing material by heating;
• and sealing the evacuation port with the sealing material deformed by being heated while an evacuated state in the internal space is maintained,
• the sealing step including supplying gas through the exhaust passage toward the evacuation port in a state where the sealing material softened by being heated blocks ventilation between the evacuation port and the internal space.