PURPOSE: To reduce the amount of processing and to conduct extraction of a moving body and calculation of the amount of movement at a high speed.

CONSTITUTION: A preceding vehicle or a white line on a road, which is taken as an object, is inputted as an image by a right image input element 1 and a left image input element 2 which are constructed of CCD cameras or the like installed so that center axes are parallel. Feature amount detecting elements 3 and 4 extract edges through filters from the images picked up by the right image input element 1 and the left image input element 2, respectively, and feature amounts extracted are sent to a differential device 5. In the differential device 5, comparison of the feature amounts obtained by the feature amount detecting elements 3 and 4 is conducted and, as the result, time-series data for the feature amounts are prepared. These time series data are stored in an image accumulating element 6 and, only prescribed parallel feature couples being observed finally in a feature amount tracing element 7, the amount of movement thereof is calculated.