A draining anti-siphon device has a water outlet pipe comprising a first water pipe and a second water pipe which are connected with each other, the pipe diameter of at least part of the second water pipe is larger than the pipe diameter of the first water pipe, one end of an air pipe is communicated with the second water pipe, and the communicating position of the air pipe and the second water pipe is located at a radial surface of the second water pipe, so that siphon reverse flow is prevented by means of a diameter changing structure of the air pipe and the water outlet pipe. In a washing machine, the draining anti-siphon device is mounted on a draining hose, the air pipe of the draining anti-siphon device is communicated with the outer drum of the washing machine.
