This dangerous item warning system is provided with an optical camera, an assessment unit, and an alerting unit. The optical camera captures an image of an object being brought into the imaging chamber of a magnetic resonance imaging device. The assessment unit, through a process that includes an image recognition process in which reference is made to previously recorded assessment information, recognizes the physical object from the image data captured by the optical camera, and generates assessment result information indicating at least whether or not the physical object is a dangerous item prohibited from being brought into the imaging chamber. The alerting unit issues alerting information on the basis of the assessment result information.