Abstract: The present invention relates to a phase separation sensor which can easily change its direction due to its flexible feature without using a corner connector even at a position limited in space or at a narrow space, and can separate and sense water and chemical solution so as to be easily used in outdoor environment exposed to rain, snow, hail or others. The phase separation sensor includes: a detection part (100) having a pair of detection lines (110, 120) spaced apart from each other in a width direction to be arranged side by side; and an insulation part (200) having insulation films (210, 220), which have detection holes (210a, 220a) formed at equal intervals in a longitudinal direction to be opposed to the detection part (100) and adhesive layers (211, 221) formed at areas of the insulation films (210, 220), which touch the detection lines (110, 120).