A protective element includes: a rectangurarly shaped insulating substrate; a heat-generating element formed on the insulating substrate; first and second electrodes laminated on a surface of the insulating substrate; first and second connecting terminals provided on a back surface of the insulating substrate and being continuous with the first and second electrodes; a heat-generating element extracting electrode provided on a current path between the first and the second electrodes and electrically connected to the heat-generating element; and a meltable conductor laminated on a region extending from the heat-generating element extracting electrode to the first and second electrodes and to be melted by heat to interrupt the current path between the first electrode and the second electrodes; wherein at least one of the corner portions of the insulating substrate is chamfered.