To obtain a power-supply alarm device capable of inhibiting the consumption of a transmitter battery by detecting battery voltage.
A transmitter 10 has a locking switch S1 and a release switch S2, and a locking or release operation code signal corresponding to operation containing an identification code is formed and transmitted from a control unit 1 by operating these switches. The feed voltage of a battery 2 conducting feed is detected by a voltage detector 3, and the locking or release operation code signal is transmitted alternately after the sending of a code signal by switch operation when the feed voltage is lower than a specific value. When a transmitted signal is received by a tuner 5 and the decision of the identification code coincides by an identification-code decision section 6, a control section 16 interprets an operation code from a received signal, a motor 7 is driven with the interpretation, and a door lock is locked and released. When the voltage of the battery 2 is low to one-time operation normally, a power-supply burden is not applied to the transmitter and a power-supply warning can be conducted by repeating locking and release.