To surely detect an opening/closing state of a door of a toilet, and to detect an abnormal condition by accurately measuring a stay time in the toilet, in an abnormal condition detection device for detecting an abnormal condition of a person in the toilet.

An abnormal condition detection device 1 for detecting an abnormal condition of a user 5 in a toilet 2 is provided with: ultrasonic sensors 12 and 13 for transmitting an ultrasonic wave from an upper part to a lower part of the toilet 2, and for receiving the reflected wave of the ultrasonic wave; a storage part 16 for storing height H1 of a door 3 of the toilet 2; an opening/closing detection part 21 for detecting the opening/closing state of the door 3 based on reception signals corresponding to the reflected waves of the ultrasonic sensors 12 and 13 and the height H1 of the door 3 in the storage part 16; and an abnormal condition decision part 23 for measuring a stay time T1 of the user 5 in the toilet 2 based on the opening/closing state of the door 3 detected by the opening/closing detection part 21, and for deciding that the user is in an abnormal condition when the stay time T1 exceeds a first permission time TS1.