To provide an effective thermally blocking composition in which a superior chemical and thermal stability is shown in a thermally blocking structure and which is non-electroconductive in a fused state, and in which a range of fusing temperature is defined.

A thermally blocking member and a composition used to produce the member have at least two organic compounds. When these compounds are fully bound, a component having a lower fusing transition temperature than that of the organic compound in the initial period before binding. The thermally blocking member is generally utilized in the thermally blocking structure having an electrically switching unit, and this electrically switching unit changes its actuation condition in case it is fused by heating up to a certain temperature against a specific material constituting the member in which the thermally blocking member is utilized.