An optical fiber temperature distribution measurement apparatus, comprising: a pulse output unit configured to output a light pulse to a selected one of a first end and a second end of an optical fiber; an intensity ratio calculation unit configured to calculate a first intensity ratio and a second intensity ratio, wherein the first intensity ratio is a ratio of Stokes light intensity to anti-Stokes light intensity obtained when the light pulse is output to the first end of the optical fiber, and the second intensity ratio is a ratio of Stokes light intensity to anti-Stokes light intensity obtained when the light pulse is output to the second end of the optical fiber; a reference temperature unit including a reference temperature optical fiber coiled in the reference temperature unit, and wherein the reference temperature unit includes a first reference thermometer configured to measure a temperature of the reference temperature optical fiber as a reference temperature; a temperature calculation unit configured to calculate a temperature distribution along the optical fiber based on the reference temperature, the first intensity ratio, the second intensity ratio, and a total length loss ratio (Ltotal), wherein the total length loss ratio (Ltotal) is a loss ratio of Stokes light intensity to anti-Stokes light intensity with regard to a total length (m) of the optical fiber; and a total length loss ratio calculation unit; characterized by a constant-temperature unit; wherein the first end of the optical fiber is connected to a first channel (CH-A) of the pulse output unit, and the second end of the optical fiber is connected to a second channel (CH-B) of the pulse output unit, wherein two predetermined sections of the optical fiber within a certain distance range from the first and second channels (CH-A, CH-B) are included in the constant-temperature unit to keep the temperature of the two predetermined sections of the optical fiber constant, and wherein the total length loss ratio calculation unit is configured to calculate the total length loss ratio (Ltotal) based on the first intensity ratio (G) and the second intensity ratio (G(m-X1)) at a predefined distance from the first and second channels (CH-A, CH-B) in the two predetermined sections. a pulse output unit configured to output a light pulse to a selected one of a first end and a second end of an optical fiber; an intensity ratio calculation unit configured to calculate a first intensity ratio and a second intensity ratio, wherein the first intensity ratio is a ratio of Stokes light intensity to anti-Stokes light intensity obtained when the light pulse is output to the first end of the optical fiber, and the second intensity ratio is a ratio of Stokes light intensity to anti-Stokes light intensity obtained when the light pulse is output to the second end of the optical fiber; a reference temperature unit including a reference temperature optical fiber coiled in the reference temperature unit, and wherein the reference temperature unit includes a first reference thermometer configured to measure a temperature of the reference temperature optical fiber as a reference temperature; a temperature calculation unit configured to calculate a temperature distribution along the optical fiber based on the reference temperature, the first intensity ratio, the second intensity ratio, and a total length loss ratio (Ltotal), wherein the total length loss ratio (Ltotal) is a loss ratio of Stokes light intensity to anti-Stokes light intensity with regard to a total length (m) of the optical fiber; and a total length loss ratio calculation unit; characterized by a constant-temperature unit; wherein the first end of the optical fiber is connected to a first channel (CH-A) of the pulse output unit, and the second end of the optical fiber is connected to a second channel (CH-B) of the pulse output unit, wherein two predetermined sections of the optical fiber within a certain distance range from the first and second channels (CH-A, CH-B) are included in the constant-temperature unit to keep the temperature of the two predetermined sections of the optical fiber constant, and wherein the total length loss ratio calculation unit is configured to calculate the total length loss ratio (Ltotal) based on the first intensity ratio (G) and the second intensity ratio (G(m-X1)) at a predefined distance from the first and second channels (CH-A, CH-B) in the two predetermined sections.