A separation device, comprising: a gas-liquid contact flow passage having a distillate discharge port formed on one end side and a bottom product discharge port formed on another end side; a raw material liquid introduction port formed between the distillate discharge port and the bottom product discharge port in the gas-liquid contact flow passage; a stripping section (130, R a, R b, R c, R d, 132), which is provided between the raw material liquid introduction port and the bottom product discharge port and is configured to heat a liquid in the gas-liquid contact flow passage; a rectification section (140, C a, C b, C c, C d, 142), which is provided between the raw material liquid introduction port and the distillate discharge port and is configured to cool a gas in the gas-liquid contact flow passage; and a heat medium unit forming flow passages (R a, R b, R c, R d,) for a first heat transfer medium in the stripping section (130, R a, R b, R c, R d, 132) and flow passages (C a, C b, C c, C d) for a second heat transfer medium in the rectification section (140, C a, C b, C c, C d, 142), wherein the separation device comprises first ribs, which extend from the raw material liquid introduction port side to the bottom product discharge portion side and second ribs, which extend from the raw material liquid introduction port side to the distillate discharge portion side, wherein the first ribs and the second ribs are arranged such that raw material liquid introduced from the raw material liquid introduction port into the gas-liquid contact flow passages flows through partitioned flow passages that are flow passages partitioned by the first and second ribs (216a, 216b) and wherein a bottom surface of the gas-liquid contact flow passage extends in an essentially horizontal direction, the bottom surface being inclined, with respect to a horizontal plane, from the distillate discharge port downward to the bottom product discharge port, characterized by a meandering flow passage forming portion, which is arranged in the gas-liquid contact flow passage and forms a meandering flow passage configured to cause a flow of the gas to meander, wherein the meandering flow passage forming portion is formed of a porous body arranged on upper surfaces of the first ribs and upper surfaces of the second ribs, an upper surface of the porous body being held in contact with a lower surface of the heat medium unit. a gas-liquid contact flow passage having a distillate discharge port formed on one end side and a bottom product discharge port formed on another end side; a raw material liquid introduction port formed between the distillate discharge port and the bottom product discharge port in the gas-liquid contact flow passage; a stripping section (130, R a, R b, R c, R d, 132), which is provided between the raw material liquid introduction port and the bottom product discharge port and is configured to heat a liquid in the gas-liquid contact flow passage; a rectification section (140, C a, C b, C c, C d, 142), which is provided between the raw material liquid introduction port and the distillate discharge port and is configured to cool a gas in the gas-liquid contact flow passage; and a heat medium unit forming flow passages (R a, R b, R c, R d,) for a first heat transfer medium in the stripping section (130, R a, R b, R c, R d, 132) and flow passages (C a, C b, C c, C d) for a second heat transfer medium in the rectification section (140, C a, C b, C c, C d, 142), wherein the separation device comprises first ribs, which extend from the raw material liquid introduction port side to the bottom product discharge portion side and second ribs, which extend from the raw material liquid introduction port side to the distillate discharge portion side, wherein the first ribs and the second ribs are arranged such that raw material liquid introduced from the raw material liquid introduction port into the gas-liquid contact flow passages flows through partitioned flow passages that are flow passages partitioned by the first and second ribs (216a, 216b) and wherein a bottom surface of the gas-liquid contact flow passage extends in an essentially horizontal direction, the bottom surface being inclined, with respect to a horizontal plane, from the distillate discharge port downward to the bottom product discharge port, characterized by a meandering flow passage forming portion, which is arranged in the gas-liquid contact flow passage and forms a meandering flow passage configured to cause a flow of the gas to meander, wherein the meandering flow passage forming portion is formed of a porous body arranged on upper surfaces of the first ribs and upper surfaces of the second ribs, an upper surface of the porous body being held in contact with a lower surface of the heat medium unit.