A glass panel unit, comprising: a first glass panel including at least a glass pane; a second glass panel disposed to face the first glass panel, the second glass panel including at least a glass pane; a seal having a frame shape and hermetically binding the first glass panel and the second glass panel together; a depressurized space surrounded by the first glass panel, the second glass panel, and the seal; and a spacer disposed between the first glass panel and the second glass panel, wherein the spacer contains a macromolecular resin material being polyimide whose thermal expansion coefficient at 400°C is lower than 10 ppm/°C, wherein the thermal expansion coefficient is measured with a thermal expansion measuring device, and including molecular chains, of the molecular chains, a number of molecular chains oriented in an orthogonal direction is larger than a number of molecular chains oriented in a counter direction, the orthogonal direction being orthogonal to the counter direction, the counter direction being a direction in which the first glass panel and the second glass panel face each other, a ratio of a thermal conductivity in the orthogonal direction to a thermal conductivity in the counter direction is higher than or equal to 1.5, the spacer is formed of a macromolecular film elongated in the orthogonal direction, a normal direction to a surface of the macromolecular film corresponding to the counter direction, an elongation ratio of the spacer in a first direction orthogonal to the counter direction is different from an elongation ratio of the spacer in a second direction orthogonal to the counter direction and the first direction, the elongation ratio of the spacer is a ratio of a length of the macromolecular film after elongation to the length of the macromolecular film before elongation, and an elongation ratio of the spacer in at least one of a first direction and a second direction is larger than or equal to 5. a first glass panel including at least a glass pane; a second glass panel disposed to face the first glass panel, the second glass panel including at least a glass pane; a seal having a frame shape and hermetically binding the first glass panel and the second glass panel together; a depressurized space surrounded by the first glass panel, the second glass panel, and the seal; and a spacer disposed between the first glass panel and the second glass panel, wherein the spacer contains a macromolecular resin material being polyimide whose thermal expansion coefficient at 400°C is lower than 10 ppm/°C, wherein the thermal expansion coefficient is measured with a thermal expansion measuring device, and including molecular chains, of the molecular chains, a number of molecular chains oriented in an orthogonal direction is larger than a number of molecular chains oriented in a counter direction, the orthogonal direction being orthogonal to the counter direction, the counter direction being a direction in which the first glass panel and the second glass panel face each other, a ratio of a thermal conductivity in the orthogonal direction to a thermal conductivity in the counter direction is higher than or equal to 1.5, the spacer is formed of a macromolecular film elongated in the orthogonal direction, a normal direction to a surface of the macromolecular film corresponding to the counter direction, an elongation ratio of the spacer in a first direction orthogonal to the counter direction is different from an elongation ratio of the spacer in a second direction orthogonal to the counter direction and the first direction, the elongation ratio of the spacer is a ratio of a length of the macromolecular film after elongation to the length of the macromolecular film before elongation, and an elongation ratio of the spacer in at least one of a first direction and a second direction is larger than or equal to 5.