A knee protection airbag apparatus (S) of this invention has an airbag (44) having a construction in which folded and accommodated below the area in front of the knees of a passenger who is seated, and inflates upward toward the rear of the vehicle so as to be capable of protecting the knees of the passenger, when an inflating gas is inserted. The airbag (44) includes a knee protection inflation portion which is disposed on the upper side of the airbag (44) after completion of inflation and which is capable of protecting both knees of the passenger, and a shin facing portion disposed below the knee protection inflation portion after completion of inflation, in an area extending substantially vertically so as to be at the position of both shins of the passenger.