PURPOSE: To control contents according to the time elapsed to prevent the error of providing deteriorated contents by providing a hot insulation time indication means for indicating the time elapsed from the start of hot insulation to be sure about the time elapsed from the start of hot insulation.

CONSTITUTION: Hot insulation is initiated by turning a power switch 24 on, and a controller 23 is cleared to its initial state to measure the time T elapsed. Operations on remaining amount and temperature retained are performed according to information inputted from a weight sensor 12 and a temperature sensor 10, for watch and control of the temperature retained. It is determined whether or not the ON control of a changeover switch 18 is performed by an even number of times. Every time the changeover switch 18 is turned on the remaining amount and the elapsed time are displayed in a liquid crystal display device 14, so when the ON control is performed by an odd number of times, the remaining amount is displayed, whereas when the number is even the elapsed time is displayed. When the determination result is affirmative (the number is even), the elapsed time T is displayed in the liquid crystal display device 14.