A heat exchanger, comprising: a plurality of flat tubes disposed in a plurality of tiers thereof, each of the flat tubes including a vertically-facing planar portion; and a plurality of fins, each being disposed in a wavily-folded state and comprised within a ventilation space interposed between two of the plurality of flat tubes, each of the two flat tubes being disposed in two given vertically-adjacent tiers of the plurality thereof, in which heat exchanger each of the plurality of fins within the ventilation space includes: a heat transfer portion having a folded portion joined to the planar portion of one of the flat tubes thereabove; and a cut-and-raised portion protruded from the ventilation space, and rising from a periphery of a cutting line segment (120, 130) at which the material of the fins is wavily folded, the cutting line segment being set in a vicinity of a hypothetical center line of the folded portion at which the material of the fins is wavily folded, characterised in that the cutting line segment is formed by any of: (a) a combination of first and second cutting line segments (121, 122) intersecting with the hypothetical center line; (b) a combination of a first cutting line segment intersecting with the hypothetical center line and a second cutting line segment displaced with respect to the hypothetical center line; or (c) a combination of first and third cutting line segments (131, 133) intersecting with the hypothetical center line and second and fourth cutting line segments (132, 134) displaced with respect to the hypothetical center line. a plurality of flat tubes disposed in a plurality of tiers thereof, each of the flat tubes including a vertically-facing planar portion; and a plurality of fins, each being disposed in a wavily-folded state and comprised within a ventilation space interposed between two of the plurality of flat tubes, each of the two flat tubes being disposed in two given vertically-adjacent tiers of the plurality thereof, in which heat exchanger each of the plurality of fins within the ventilation space includes: a heat transfer portion having a folded portion joined to the planar portion of one of the flat tubes thereabove; and a cut-and-raised portion protruded from the ventilation space, and rising from a periphery of a cutting line segment (120, 130) at which the material of the fins is wavily folded, the cutting line segment being set in a vicinity of a hypothetical center line of the folded portion at which the material of the fins is wavily folded, a heat transfer portion having a folded portion joined to the planar portion of one of the flat tubes thereabove; and a cut-and-raised portion protruded from the ventilation space, and rising from a periphery of a cutting line segment (120, 130) at which the material of the fins is wavily folded, the cutting line segment being set in a vicinity of a hypothetical center line of the folded portion at which the material of the fins is wavily folded, characterised in that the cutting line segment is formed by any of: (a) a combination of first and second cutting line segments (121, 122) intersecting with the hypothetical center line; (b) a combination of a first cutting line segment intersecting with the hypothetical center line and a second cutting line segment displaced with respect to the hypothetical center line; or (c) a combination of first and third cutting line segments (131, 133) intersecting with the hypothetical center line and second and fourth cutting line segments (132, 134) displaced with respect to the hypothetical center line. (a) a combination of first and second cutting line segments (121, 122) intersecting with the hypothetical center line; (b) a combination of a first cutting line segment intersecting with the hypothetical center line and a second cutting line segment displaced with respect to the hypothetical center line; or (c) a combination of first and third cutting line segments (131, 133) intersecting with the hypothetical center line and second and fourth cutting line segments (132, 134) displaced with respect to the hypothetical center line.