A coefficient-of-thermal-expansion measurement method of a measurement target in a form of a dimension reference gauge, a coefficient-of-thermal-expansion of a measurement target section of the measurement target being measured in the method, the method comprising: providing: a reference gauge (20E, 20F) having a known reference gauge length (Dr) that is shorter than a length (Dt) of the measurement target section; a temperature-controlled chamber configured to adjust an interior temperature thereof and to house the measurement target and the reference gauge (20E, 20F), the temperature-controlled chamber comprising a measurement surface provided with a measurement aperture; and a coordinate measuring machine comprising a measurement probe that is introducible into an inside of the temperature-controlled chamber through the measurement aperture; allocating a plurality of relative measurement sections (M1, M2, M3) each having a length corresponding to the reference gauge length (Dr) to the measurement target section, each of the plurality of relative measurement sections (M1, M2, M3) being shifted by a predetermined shift amount (Dd); supporting the measurement target and the reference gauge (20E, 20F) in parallel in the inside of the temperature-controlled chamber; setting the interior temperature of the temperature-controlled chamber at a first temperature; sequentially performing a first relative measurement of the length (Dt11, Dt21, Dt31) of each of the plurality of relative measurement sections (M1, M2, M3) with reference to the reference gauge (20E, 20F); setting the interior temperature of the temperature-controlled chamber at a second temperature; sequentially performing a second relative measurement of the length (Dt12, Dt22, Dt32) of each of the plurality of relative measurement sections (M1, M2, M3) with reference to the reference gauge (20E, 20F); calculating section coefficient-of-thermal-expansions of the plurality of relative measurement sections (M1, M2, M3) based on the length (Dt11, Dt21, Dt31) obtained by the first relative measurement at the first temperature and the length (Dt12, Dt22, Dt32) obtained by the second relative measurement at the second temperature for each of the relative measurement sections (M1, M2, M3); and calculating a coefficient-of-thermal-expansion of an entirety of the measurement target section based on the calculated section coefficient-of-thermal-expansions of the plurality of relative measurement sections. providing: a reference gauge (20E, 20F) having a known reference gauge length (Dr) that is shorter than a length (Dt) of the measurement target section; a temperature-controlled chamber configured to adjust an interior temperature thereof and to house the measurement target and the reference gauge (20E, 20F), the temperature-controlled chamber comprising a measurement surface provided with a measurement aperture; and a coordinate measuring machine comprising a measurement probe that is introducible into an inside of the temperature-controlled chamber through the measurement aperture; allocating a plurality of relative measurement sections (M1, M2, M3) each having a length corresponding to the reference gauge length (Dr) to the measurement target section, each of the plurality of relative measurement sections (M1, M2, M3) being shifted by a predetermined shift amount (Dd); supporting the measurement target and the reference gauge (20E, 20F) in parallel in the inside of the temperature-controlled chamber; setting the interior temperature of the temperature-controlled chamber at a first temperature; sequentially performing a first relative measurement of the length (Dt11, Dt21, Dt31) of each of the plurality of relative measurement sections (M1, M2, M3) with reference to the reference gauge (20E, 20F); setting the interior temperature of the temperature-controlled chamber at a second temperature; sequentially performing a second relative measurement of the length (Dt12, Dt22, Dt32) of each of the plurality of relative measurement sections (M1, M2, M3) with reference to the reference gauge (20E, 20F); calculating section coefficient-of-thermal-expansions of the plurality of relative measurement sections (M1, M2, M3) based on the length (Dt11, Dt21, Dt31) obtained by the first relative measurement at the first temperature and the length (Dt12, Dt22, Dt32) obtained by the second relative measurement at the second temperature for each of the relative measurement sections (M1, M2, M3); and calculating a coefficient-of-thermal-expansion of an entirety of the measurement target section based on the calculated section coefficient-of-thermal-expansions of the plurality of relative measurement sections.