A funnel for a water tank is for adapting to a water injection portion. The water injection portion is communicated with the water tank. The funnel includes a container body and a valve assembly. The container body has an inner wall, an abutting portion, an internal space, and an injection opening and an output opening which are communicated with the internal space. The valve assembly is abuttable against the abutting portion. The valve assembly includes an actuating member communicated with the output opening and a valve body which is coupled with the actuating member. When the actuating member is located in a first position, the container body is uncommunicated with the interior of the water tank. When the actuating member is away from the first position, the container body is communicated with the water tank to allow liquid flow into the water tank.