PURPOSE: To obtain an automatic gas shutoff unit which enables sensing of an extraordinarily high temperature and automatic shutoff of gas, by installing the gas shutoff unit in a peripheral place of a gas appliance where a solid holder is not fused ordinarily, but is fused when it is heated.

CONSTITUTION: A gas shutoff unit is installed in a peripheral place of a gas appliance where a solid holder 11 is not fused in an ordinary state of use, but is fused when it is heated by extraordinary radiant heat. In a normal state of use, according to this constitution, a through hole 13 of a valve plug 7 is made to communicate with a gas passage 3 by the solid holder 11. When a pot or the like is heated for some reason and the solid holder 11 of hot-melt properties is fused by the radiant heat thereof through a cap 27, the valve plug 7 is pulled to move by a spring 9, since the spring functions constantly, thereby shutting off the gas passage 3. In order to reset the gas shutoff unit, it is needed only to remove the fused holder with the cap 27 taken off, to pull up the valve plug against the spring 9 and to put in a fresh holder to a prescribed position.