A proximity alarm device includes a control unit, an amplifying unit, an output terminal, a ground terminal, a detection unit, and a determining apparatus. The control unit receives an input of a referencing signal. An output of the control unit is electrically connected to the amplifying unit. An output of the amplifying unit is electrically connected to an output terminal. The ground terminal is electrically connected to a ground. The output of the amplifying unit is electrically connected to the detection unit. An output of the detection unit is electrically connected to the determining apparatus. Then, the determining apparatus compares a detection signal detected by the detection unit and a determination reference signal with each other.