PURPOSE: To provide a trouble monitoring device for a heating apparatus which enables detection of the trouble in the A/D converter of a temperature control device comprising a microcomputer.

CONSTITUTION: The circuit trouble monitoring means of a temperature control device comprising a one-chip microcomputer 40 with a built-in A/D converter stops operation of a heating apparatus when, in an inspecting signal VD having a level lower than the minimum level of a temperature signal VT from a temperature sensor 6, the VT is lower than VD. An A/D converter trouble monitoring means causes a monitoring circuit 44 to output an inspection signal having a level lower than that of the VD at every interval T. When the inspection signal can not be identified by the circuit trouble monitoring means, operation of a heating apparatus is stopped.