Provided is an apparatus capable of, even when an object is moving, measuring the position of the object at a high accuracy. According to a vehicle periphery monitoring apparatus (10), an enlargement factor relevant to when the degree of correlation between an enlarged local region (EB(γi)) obtained by enlarging a local region (B(k−1)) at a previous time (k−1) and a local region (B(k)) at a time (k) later than the previous time (k−1) becomes the maximum is calculated as a change rate (Rate(k)) of the size of the local region (B(k)). Based on the change rage (Rate(k)), it is possible to measure the distance (Z(k)) from a vehicle (1) to the object or the position (P(k)) at a high accuracy even when the object is moving.