A voltage detecting circuit included in a battery device includes an input voltage comparing circuit that compares a first threshold value voltage or a second threshold value voltage lower than the first threshold value voltage with an input voltage to control the opening and closing of an output switching element, and a threshold value voltage setting circuit that compares a third threshold value voltage lower than the second threshold value voltage with the input voltage and, when the input voltage changes from a low voltage to a high voltage and intersects the third threshold value voltage, outputs a pulse for a predetermined period thereafter so that the second threshold value is selected in the input voltage comparing circuit. As a result, when the input voltage increases from the ground potential, the second threshold value is compared with the input voltage in the input voltage comparing circuit. The voltage detecting circuit and battery device using the circuit, when assembled in battery using equipment, uses a battery up to its usage limit.