Provided is a detection method of a detection device. The detection device detects at least one object from an image by using depth information about the image obtained by a camera. The detection device identifies whether said at least one object is a person through three-dimensional (3D) head model matching, which matches a head candidate area of said at least one object with a 3D head model. The detection device calculates a feature for detection of a situation by using said at least one object when it is identified that said at least one object is the person.