A sound absorbing structure is constituted of a vibration plate and a rear air layer and is installed in a luggage compartment or trunk which is separated from a cabin in a vehicle. Sound waves entering into the luggage compartment drive the vibration plate to vibrate so that acoustic energy is converted into mechanical energy and is consumed by way of vibration of the vibration plate. By appropriately setting parameters and dimensions, the sound absorbing structure efficiently absorbs low-frequency sound such as road noise occurring due to friction of wheels of the vehicle traveling on a road.