A multiple-piece vacuum-insulated heating tank for use in a water dispenser includes a threaded cover, a thermal insulation cover, and a heating tank body. The threaded cover is mounted on an upper opening of the heating tank body and includes a plastic cover and a protective cover mounted on and around the plastic cover. The thermal insulation cover is fitted in the upper opening and includes an upper cover and a lower cover. The lower cover is cup-shaped; is mounted with a heating tube, a water inlet pipe, a water outlet pipe, a thermowell, a temperature-sensing heat pipe, a heat collector block, and two snap-action thermostats at the bottom side; and has a sidewall formed with a step adjacent to the bottom side. The heating tank not only has a multiple-piece structure that facilitates mass production and maintenance, but also dispenses with electronic temperature control as is conventionally required.