To avoid a detection signal being output erroneously, in a low-voltage detecting circuit which includes a constant voltage circuit that generates such a reference voltage as to change in the form of staircase, to the linear change of a power voltage.

This low-voltage detecting circuit includes a constant voltage circuit (33), which generates a reference voltage at a prescribed potential, and a voltage comparing means (32), which determines whether the power voltage is higher or lower than the prescribed potential by comparing the voltage proportionate to the power voltage with the reference voltage and outputs a detection signal on a first level in case that it is high and on a second level in case that it is low. The constant voltage circuit generates the reference voltage having such properties as to be in the shape of staircase to the linear change of the power voltage, and there is a risk that the voltage comparing means might output an erroneous detection signal in a region where the power voltage is lower than the prescribed potential. This low-voltage detecting circuit includes an erroneous operation range detecting circuit (34), which detects the power voltage being in a range that an erroneous detection signal arises, thereby being so structurized as to inhibit the output of the detection signal from the voltage comparing means.