1. A vehicle environment recognizing apparatus comprising: an image capturing device configured to capture an image of a road on which a vehicle is traveling; a road shape calculating section configured to calculate approximation lines that approximate a shape of the road in at least two regions that are located at different distances in front of the vehicle based on image data captured by the image capturing device; a straight road determining section configured to determine whether the road on which the vehicle is traveling is straight based on a degree to which the approximation lines of the regions calculated by the road shape calculating section match one another; a parallel travel determining section configured to determine whether the vehicle is traveling parallel to the road based on a detection result determined from the image data captured by the image capturing device and the approximation lines calculated by the road shape calculating section; an imaginary vanishing point calculating section configured to calculate an imaginary vanishing point using an intersection point between a left approximation line and a right approximation line of the approximation lines upon determining that the road on which the vehicle is traveling is straight and that the vehicle is traveling parallel to the road; and an optical axis direction revising section configured to estimate an estimated optical axis direction of the image capturing device based on a calculation result of the imaginary vanishing point calculating section and revise a preset value of an optical axis direction.