An object detecting apparatus for a vehicle has a light radiation unit, a reflection mirror, a polygon mirror, a light reception unit, all disposed in a case. The apparatus further has a position adjusting device for adjusting the reflection mirror to a first position to reflect the light toward the scanning mirror or to a second position not to reflect the light toward the scanning mirror, and a light conducting member for conducting the light passing through the reflection mirror to the reception unit. The light conducting member has one end positioned opposite the radiation unit with respect to the reflection mirror.