An abnormality detection apparatus for detecting an event where a monitored object in a room has lapsed into an abnormal state. The apparatus includes an image pickup system for picking up an image of a scene in the room, and feature-quantity extraction devices for extracting an image feature quantity from the image picked up by the image pickup devices. The apparatus also includes judgment devices for determining whether the monitored object in the room has lapsed into the abnormal state or not based on the time-variations of the image feature quantity extracted by the feature-quantity extraction devices, and outputting an alarm that responds to the determination of the occurrence of the abnormal state.