To improve the hot-keeping state of boiled rice at low temperatures and heat up the boiled rice to the normal hot-keeping temperature when it is served to prevent the savor of the boiled rice from deteriorating, by a method wherein the boiled rice is selectively kept at two or more hot-keeping temperatures and the hot-keeping temperature is switched from the low-temperature over to the high-temperature at line specified reservation time.

When a rice cooking operation by a rice cooking controller 71 finishes, a hot-keeping controller 72 starts a normal hot-keeping operation controlled by a normal hot- keeping controller 73 at first. When a hot-keeping switch 25B is operated, a low-temperature hot-keeping operation controlled by a low-temperature hot-keeping controller 74 starts, and a reservation time at which the low-temperature hot-keeping operation is switched over to a normal hot-keeping operation, for example, the time six hours from now, is indicated on a reservation time indicator 23B. The low-temperature hot-keeping operation controlled by the low-temperature hot-keeping controller 74 lasts until an hour before the reservation time stored in a reservation device 76. When the time is over, the hot-keeping controller 72 switches the hot-keeping operation to normal hot-keeping operation controlled by the normal hot-keeping controller 73. When the reservation time comes after six hours since the low-temperature hot-keeping operation starts, the reservation operation by the hot-keeping control reservation device 75 is completed.