Heat exchange device and gas water heater

The invention discloses a heat exchange device and a gas water heater. The heat exchange device comprises a heat exchange cavity shell and multiple heat exchange straight pipes. The heat exchange straight pipes are connected in series through elbows to form a heat exchange passageway. The water inlet end of the heat exchange passageway is connected with a water inlet pipe. The water outlet end ofthe heat exchange passageway is connected with a water outlet pipe. The heat exchange straight pipes are horizontally arranged and are arranged into at least two layers in the vertical direction. Thetwo ends of each elbow are connected with the two corresponding heat exchange straight pipes located on different layers correspondingly. According to the heat exchange device, the heat exchange straight pipes are arranged into at least two layers in the vertical direction, the two ends of each elbow are connected with the two corresponding heat exchange straight pipes located on the different layers correspondingly, and i