An image forming device is provided to be able to make efficient use of an internal space while improving the detection accuracy, with which a detected body is detected. The image forming device according to the invention comprises a housing, a duct, through which an air in the housing is caused to flow, a detection portion arranged outside the duct to be displaced according to the presence of, or movement of a detected body, an operating portion that can be displaced in the duct, a detection element arranged in the duct to detect displacement of the operating portion, and a transmission portion that transmits displacement of the detection portion to the operating portion through an opening formed on the duct.