Provided are: a drainage device with which the timing of drainage can be controlled; and a drainage
system equipped with the same. The drainage device is characterized by comprising a
siphon mechanism 2 that is provided inside a water tank 1, and is constituted from a
siphon pipe 20 and a cylindrical part 30. The drainage device is also characterized in that: one end side of the
siphon pipe 20 has a first opening part 21a that is open at the top part thereof, and the other end side has a first connection part 24a that is connected to an overflow
pipe 3; the cylindrical part 30 has a second opening part 21b of which the inner
diameter is larger than that of the siphon pipe 20, into which the first opening part 21a of the siphon pipe 20 is inserted, and which is open at the bottom part thereof; the second opening part 21b is set at a position lower than the first opening part 21a; and a second connection part 30b, which is for selectively connecting the inside of the cylindrical part to an
air pump 5 or to the
atmosphere, is provided to the top surface of the cylindrical part 30.