A heating device includes a heater, an AC-voltage input section between which an AC voltage is applied, a fuse, a switcher, an AC-voltage-abnormality detector configured to detect an abnormality of the AC voltage, a controller. The controller is configured to execute a current-flowing operation in a state in which connection of a first connection terminal to a second connection terminal is a non-connecting state. The current-flowing operation is an operation in which an electrical current flows through the heater. The controller is configured to execute a connecting process in response to detection of the abnormality of the AC voltage by the AC-voltage-abnormality detector detected in the middle of the current-flowing operation. The connecting process is a process of switching a connection of a first connecting point to a second connecting point from a non-connecting state to a connecting state.