Embodiments relate to a Brillouin distributed optical fiber sensor including a first light source to output a first light having a modulated intensity at a preset frequency, an optical modulation unit to generate Brillouin probe light and Brillouin pump light using the first light and apply the Brillouin probe light and the Brillouin pump light to one end and the other end of a test optical fiber, respectively, a second light source to apply a second light with a frequency that is different from a frequency of the first light to one end of the test optical fiber in a direction opposite to the Brillouin pump light, and an optical detection unit to detect Brillouin scattered light generated by interaction between the Brillouin pump light and the Brillouin probe light in the test optical fiber.