1. An automotive environment monitoring device which monitors environment of a vehicle by using an image obtained from an imaging unit mounted on the vehicle, comprising: a first processing unit which sets an area where an object exists in the image obtained from the imaging unit as a first area and a lower portion of the first area as a second area; a second processing unit which extracts a positive or negative edge line, and a length of each of the positive or negative edge line of the object in the second area set by the first processing unit as a feature of the object in the second area set by the first processing unit; and a third processing unit which identifies the object as a human on a condition that at least three positive or negative edge lines with the length in a first length range are extracted by the second processing unit on the basis of an extraction result by the second processing unit.