A knee airbag apparatus includes a folded airbag. The folded airbag includes an upper folded part formed by rolling an upper end of the airbag toward a lower end of the airbag after the upper end of the airbag is folded on the front panel; and a lower folded part disposed to be adjacent to the upper folded part by folding at least once a lower portion of the airbag in a direction that is opposite to the rolling direction of the upper folded part. The folded airbag includes a side folded part formed by folding a side portion of the airbag before the upper folded part is formed or by folding both sides of the upper and lower folded parts after the upper and lower folded parts are formed.