An object detector for accurately detecting a still object. Normative flow creating means (2) creates a normative flow of a screen supposed in a normal environment where no object is present according to the installed state of imaging means (3) installed in a vehicle and the traveling state of the vehicle. Observation flow creating means (4) creates an observation flow according to the image captured by imaging means. Comparing/checking section (5) detects an object on the basis of the difference between the normative flow created by the normative flow creating means and the observation flow created by the observation flow creating means.
