To provide a ranging sensor whose structure is simplified, and which is high in accuracy.

The ranging sensor has at least two light-emitting devices that project light to an object to be ranged, and one light-receiving element for receiving the light that is reflected by the object to be ranged. Each of the light-emitting devices and the light-receiving element is placed on the same base line long a axis in parallel. At the same time, one light-emitting device is arranged at a position, where the light emission is reflected on the object to be ranged at a close side and can be received by the light-receiving element, and the other is arranged at a position where the emitted light is reflected at the object to be ranged at a far side and can be received by the light- receiving element, thus providing at least two distances to be ranged.