According to one embodiment, a user detection system includes a camera, a boundary detector, a user detector and a controller. The camera is installed in a peripheral region of a door, and captures a running region when opening or closing the door and a region near the door. The boundary detector detects a boundary between a first structure and a second structure in the region near the door based on an image captured by the camera. The user detector detects whether there is a user in the running region based on a result detected by the boundary detector. The controller controls an open/close operation of the door based on a result detected by the user detector.