A state switching device for switching the states of a device by detecting a battery voltage of the device is provided. The device includes a voltage dividing circuit to provide an output voltage in proportion to the battery voltage, and a detection unit which includes a voltage detection module, a comparison module, a control module and a state detection module to obtain the device's state. The voltage detection module produces a digital detection voltage according to the output voltage at normal time intervals, the comparison module detects whether the digital detection voltage is lower than a reference voltage corresponding to the state. If yes, the voltage detection module obtains digital detection voltage at abnormal time intervals. The comparison module compares a predetermined number of digital detection voltages with the reference voltage to produce comparison results. The control module determines whether to maintain the device's state according to the comparison results.