Three-way adjusting device and gas water heater

The invention belongs to the technical field of gas water heaters, and discloses a three-way adjusting device and a gas water heater. The three-way adjusting device comprises a valve body, a mandrel and a driving part, the valve body is provided with a valve cavity, and a main water inlet, a main water outlet and a bypass water outlet which can be communicated with the valve cavity are formed in the valve body; the core shaft is arranged in the valve cavity in a penetrating manner; a first valve element protruding in the circumferential direction is arranged on the mandrel in the axial direction of the mandrel and located between the main water outlet and the bypass water outlet. The driving piece is configured to drive the core shaft to move in the valve cavity in the axial direction; when the mandrel moves in the axial direction, one of the opening degree A of the main water outlet and the opening degree B of the bypass water outlet is gradually decreased while the other one is synchronously and gradually i