A kettle has a container and a guiding board. The container has a body. The body has an upper segment, a lower segment, and a through hole defined in the lower segment and having a top edge and a bottom edge. The guiding board is attached securely to an inner surface of the lower segment of the body, covers the through hole, and has a guiding segment. The guiding segment is attached securely to the inner surface of the lower segment of the body at a position below the bottom edge of the through hole, is curved in cross section, extends upward and toward the central line of the body, is free from forming a through bore, and has a top edge higher than the bottom edge of the through hole and lower than the top edge of the through hole.

Provided is a cooking appliance configured to maintain heat retention of contents. The cooking appliance is configured to, when entering a heat retention mode, compare a temperature of the contents measured via a temperature sensor with a target heat retention temperature, and when the temperature of the contents is equal to or greater than the target heat retention temperature, transmit power control information to a wireless power transmission device, the power control information indicating to suspend transmission of first power and then to re-transmit the first power after an elapse of a preset time.