The present invention provides a hinge structure for an air bag door. The hinge structure includes a housing disposed inside a crash pad, an air bag disposed inside the housing, an air bag door disposed on a rear surface of the crash pad adjacent to the air bag, a hinge portion disposed on at least a portion of a rear surface of the air bag door, and a scrim member disposed at least a portion of the hinge portion, the housing and the air bag door, all the components constituting an air bag assembly, wherein the hinge portion is constructed so as to break when the air bag door is opened, and the scrim member serves to enable the air bag door to be opened while being connected to the housing after the hinge portion breaks.