PURPOSE: To enable exchange only at desired timing by providing a liquid heat insulating vessel having a water cleaning function with an exchange timing judging means for judging the exchange timing of a water cleaning filter and an alarming means for alarming the exchange timing of the water cleaning filter based on the judgement of the exchange timing judging means.

CONSTITUTION: Water cleaning time PT is measured. However, this water cleaning time PT is not directly measured but hot-water boiling time, namely, time for energizing to a heater 3 for hot-water boiling is measured. Thus, even when the time for energizing to the heater 3 for hot-water boiling is measured, water in an inner vessel 2 is circulated from a water-raising pipe 5 and a water cleaning pipe 7 through a water cleaning filter 9 by a water-raising pump 6 during the hot-water boiling time and the hot-water boiling time is decided corresponding to the quantity of water in the inner vessel 2 so that the water cleaning time PT can be measured as a result. The measured water cleaning time PT is added to previous use time FT of the water cleaning filter 9. It is judged whether the total value of the water cleaning time PT exceeds a set value G or not. The set value G is previously decided numerical value to require the exchange of the filter 9.