A vehicular orientation detection system for detecting an orientation of a vehicle traveling on a road surface where magnetic markers positioned as separated in a route direction of a traveling road are laid, the system comprising: a lateral shift amount measurement part which detects a magnetic marker and measures a lateral shift amount with respect to the magnetic marker; characterized by a lateral shift amount difference acquiring part which obtains a difference between lateral shift amounts measured with the same magnetic marker by a plurality of said lateral shift amount measurement parts positioned at at least two locations separated in a longitudinal direction of the vehicle, wherein the detection of the orientation is performed when the difference between the lateral shift amounts measured by any one of the lateral shift amount measuring parts with two of the magnetic markers positioned as separated in the route direction of the traveling road is smaller than a predetermined threshold, and/or wherein the system comprises a steering angle measurement part which measures a steering angle that indicates a steering direction of a steering wheel equipped in the vehicle, and the detection of the orientation is performed when a change amount of the steering angle per unit time is smaller than a predetermined threshold, and/or wherein the detection of the orientation is performed when a change amount of the vehicle in a traveling direction per unit time is smaller than a predetermined threshold, and/or wherein the system comprises a route data acquiring part which acquires route data representing a route direction of a traveling road, a steering angle measurement part which measures a steering angle that indicates a steering direction of a steering wheel equipped in the vehicle, and a direction comparison part which computes a degree of coincidence between the route direction represented by the route data and the steering direction corresponding to a measurement value of the steering angle, and the detection of the orientation is performed when the degree of coincidence is equal to or larger than a predetermined threshold. a lateral shift amount measurement part which detects a magnetic marker and measures a lateral shift amount with respect to the magnetic marker; characterized by a lateral shift amount difference acquiring part which obtains a difference between lateral shift amounts measured with the same magnetic marker by a plurality of said lateral shift amount measurement parts positioned at at least two locations separated in a longitudinal direction of the vehicle, wherein the detection of the orientation is performed when the difference between the lateral shift amounts measured by any one of the lateral shift amount measuring parts with two of the magnetic markers positioned as separated in the route direction of the traveling road is smaller than a predetermined threshold, and/or wherein the system comprises a steering angle measurement part which measures a steering angle that indicates a steering direction of a steering wheel equipped in the vehicle, and the detection of the orientation is performed when a change amount of the steering angle per unit time is smaller than a predetermined threshold, and/or wherein the detection of the orientation is performed when a change amount of the vehicle in a traveling direction per unit time is smaller than a predetermined threshold, and/or wherein the system comprises a route data acquiring part which acquires route data representing a route direction of a traveling road, a steering angle measurement part which measures a steering angle that indicates a steering direction of a steering wheel equipped in the vehicle, and a direction comparison part which computes a degree of coincidence between the route direction represented by the route data and the steering direction corresponding to a measurement value of the steering angle, and the detection of the orientation is performed when the degree of coincidence is equal to or larger than a predetermined threshold.