A heating device includes a heater, a holder, a connector, and a guide pair. The heater includes an electrode through which power is conducted. The holder is configured to hold the heater. The connector includes a conduction terminal and an engagement portion. The conduction terminal is configured to contact the electrode. The engagement portion is configured to be engaged with the holder. The connector is attachable to the holder to engage the engagement portion with the holder and contact the conduction terminal with the electrode. The guide pair includes a convex portion and a recess. The convex portion is disposed in one of the holder and the connector. The recess is disposed in another one of the holder and the connector. The guide pair is configured to guide the connector in an attaching direction of the connector to attach the connector to the holder.