1. A rearview monitoring apparatus for a vehicle for displaying a rearview image which is taken by a camera for covering a rearview of the vehicle to occupants in the vehicle comprising: a vehicle index storing device for storing a vehicle index representing a vehicle's protruding region which protrudes over a rear reference position of the vehicle in advance; a superposed image displaying device for superposing the vehicle index onto the vehicle's protruding region in the rearview image according to the position of the vehicle's protruding region.