An alarm apparatus includes an electric conductor disposed at a window pane, a voltage supply device that supplies a voltage to the electric conductor, a voltage detection device that detects the voltage of the electric conductor, a disconnection determination device that makes a determination regarding a disconnected state of the electric conductor based on the detected voltage of the electric conductor, an alarm determination device that determines whether or not to perform alarming based on a result of determination of the disconnection determination device; and an alarm device that performs the alarming based on the determination by the alarm determination device. The alarm determination device has an alert mode of performing if the electric conductor is in the disconnected state, and a pre-alert mode of refraining from performing the alarming if the electric conductor is in the disconnected state.
