A manufacturing method for a glass panel unit comprising: a placing step of placing a first glass substrate and a second glass substrate to face each other with a seal member including a frame member with a frame shape in-between; a bonding step of bonding the first glass substrate and the second glass substrate to each other with the seal member, and forming an inside space enclosed by the frame member between the first glass substrate and the second glass substrate bonded to each other with the frame member; a treatment step of evacuating air from the inside space or supplying gas to the inside space; and a cutting step of cutting the first glass substrate, the seal member, and the second glass substrate collectively along a cut plane imaginary passing through the seal member from one of the first glass substrate and the second glass substrate bonded to each other; characterized in that: at least one of the first glass substrate and the second glass substrate includes a vent; the seal member further includes a partition member; the bonding step includes partioning by the partition member the inside space into a first space directly connected to the vent and a second space not directly connected to the vent, and providing one or more gas passages for allowing gas to move between the first space and the second space; the treatment step includes evacuating air from the inside space or supplying gas to the inside space, through the vent, and then closing the one or more gas passages to hermetically enclose the first space; and the cutting step includes cutting the first glass substrate, the partition member, and the second glass substrate collectively along the cut plane passing through the partition member, and dividing the first glass substrate, the partition member, and the second glass substrate into a part used as a panel unit including the first space and an unnecessary part including the second space and the vent. a placing step of placing a first glass substrate and a second glass substrate to face each other with a seal member including a frame member with a frame shape in-between; a bonding step of bonding the first glass substrate and the second glass substrate to each other with the seal member, and forming an inside space enclosed by the frame member between the first glass substrate and the second glass substrate bonded to each other with the frame member; a treatment step of evacuating air from the inside space or supplying gas to the inside space; and a cutting step of cutting the first glass substrate, the seal member, and the second glass substrate collectively along a cut plane imaginary passing through the seal member from one of the first glass substrate and the second glass substrate bonded to each other; characterized in that: at least one of the first glass substrate and the second glass substrate includes a vent; the seal member further includes a partition member; the bonding step includes partioning by the partition member the inside space into a first space directly connected to the vent and a second space not directly connected to the vent, and providing one or more gas passages for allowing gas to move between the first space and the second space; the treatment step includes evacuating air from the inside space or supplying gas to the inside space, through the vent, and then closing the one or more gas passages to hermetically enclose the first space; and the cutting step includes cutting the first glass substrate, the partition member, and the second glass substrate collectively along the cut plane passing through the partition member, and dividing the first glass substrate, the partition member, and the second glass substrate into a part used as a panel unit including the first space and an unnecessary part including the second space and the vent. at least one of the first glass substrate and the second glass substrate includes a vent; the seal member further includes a partition member; the bonding step includes partioning by the partition member the inside space into a first space directly connected to the vent and a second space not directly connected to the vent, and providing one or more gas passages for allowing gas to move between the first space and the second space; the treatment step includes evacuating air from the inside space or supplying gas to the inside space, through the vent, and then closing the one or more gas passages to hermetically enclose the first space; and the cutting step includes cutting the first glass substrate, the partition member, and the second glass substrate collectively along the cut plane passing through the partition member, and dividing the first glass substrate, the partition member, and the second glass substrate into a part used as a panel unit including the first space and an unnecessary part including the second space and the vent.