To provide a mobile warmer which shows an insignificant temperature drop even when a door is operated ON/OFF during the movement of the warmer following the shutoff of power supply.

This mobile warmer 100 is caused to generate heat by an electric heating source 103 which warms the interior of a heat-retaining box 101 and the electric heat source 12 of a heat accumulator 10 using a power supply from a power supply plug 110. The electric heat source 103 directly warms the interior of the heat- retaining box 101 at about 80°C and the electric heat source 12 heats a heat accumulating material 11 at about 30°C. The mobile warmer 100 is moved under such a state that a power supply is cut off by pulling the power supply plug 110 out of a power supply outlet, and therefore, the internal temperature of the warmer 100 drops due to the ON/OFF operation of a door. The internal air of the heat-retaining box 101 is circulated through a route starting with a suction aperture and ending with a blowout aperture 18B passing through flow paths 14a-14 with the help of a ventilator 15 driven by a secondary cell. The internal air of the heat-retaining box 101 is warmed by giving a quantity of heat to the air from the heat accumulator 11, so that the loss of the heat is compensated for. Thus it is possible to retain heat for a long time. The circulating air can be brought into contact directly with the surface of the heat accumulating material 11 as an alternative choice.