An object detecting apparatus comprising: a light source configured to emit light, a deflecting unit configured to rotate around a rotational axis and have at least two reflecting faces (14a, 14b, 14c, 14d), to deflect the emitted light with the reflecting faces to cause the emitted light to scan a predefined range of an object, and to deflect light returning from the predefined range of the object, an image forming unit, and a light detecting device configured to detect the returning light deflected by the reflecting faces through the image forming unit, wherein the at least two reflecting faces are placed in a three-dimension orthogonal coordinate system in which the X axis is directed from the rotational axis of the deflecting unit to a center of the predefined range, the Y axis is directed in a scanning direction of the deflecting unit, and the Z axis is directed in an axial direction of the rotational axis of the deflecting unit, and a travel direction of the emitted light incident on the reflecting faces is parallel to an X-Y plane and a travel direction of the returning light deflected by the reflecting faces, which is to be transmitted orthogonal onto a center of a receiving surface of the light detecting device, is parallel to the X-Y plane, characterized in that: the at least two reflecting faces have different inclining angles with respect to the rotational axis of the deflecting unit, the travel direction of the emitted light incident on the reflecting faces is at an angle of less than 90 degrees with respect to the X axis, and the travel direction of the returning light deflected by the reflecting faces is at an angle of less than 90 degrees with respect to the X axis. a light source configured to emit light, a deflecting unit configured to rotate around a rotational axis and have at least two reflecting faces (14a, 14b, 14c, 14d), to deflect the emitted light with the reflecting faces to cause the emitted light to scan a predefined range of an object, and to deflect light returning from the predefined range of the object, an image forming unit, and a light detecting device configured to detect the returning light deflected by the reflecting faces through the image forming unit, wherein the at least two reflecting faces are placed in a three-dimension orthogonal coordinate system in which the X axis is directed from the rotational axis of the deflecting unit to a center of the predefined range, the Y axis is directed in a scanning direction of the deflecting unit, and the Z axis is directed in an axial direction of the rotational axis of the deflecting unit, and a travel direction of the emitted light incident on the reflecting faces is parallel to an X-Y plane and a travel direction of the returning light deflected by the reflecting faces, which is to be transmitted orthogonal onto a center of a receiving surface of the light detecting device, is parallel to the X-Y plane, characterized in that: the at least two reflecting faces have different inclining angles with respect to the rotational axis of the deflecting unit, the travel direction of the emitted light incident on the reflecting faces is at an angle of less than 90 degrees with respect to the X axis, and the travel direction of the returning light deflected by the reflecting faces is at an angle of less than 90 degrees with respect to the X axis. the at least two reflecting faces have different inclining angles with respect to the rotational axis of the deflecting unit, the travel direction of the emitted light incident on the reflecting faces is at an angle of less than 90 degrees with respect to the X axis, and the travel direction of the returning light deflected by the reflecting faces is at an angle of less than 90 degrees with respect to the X axis.