A waste disposal device for an aircraft lavatory unit, comprising: a waste compartment adapted to be provided on a floor of the aircraft lavatory unit installed in an aircraft and comprising an opening portion through which a waste container is taken in and out; a chute provided in an upper portion of the waste compartment and comprising a trash feeding opening; and a waste flap swingably supported by the chute between a closed position for closing the trash feeding opening and an opened position for opening the trash feeding opening and biased in a direction of closing the trash feeding opening; a foot pedal adapted to be disposed close to a section on the floor directly below the waste compartment; a foot pedal-type waste flap opening/closing mechanism configured to swing the waste flap from the closed position to the opened position by stepping on the foot pedal, the foot pedal-type waste flap opening/closing mechanism comprising a foot pedal support mechanism that swingably supports the foot pedal between an upper limit position at which the foot pedal is configured to be stepped on and a lower limit position at which the foot pedal is stepped on from the upper limit position and biases the foot pedal allowing the foot pedal to be located at the upper limit position, and the foot pedal support mechanism being configured such that the foot pedal at the upper limit position is inclined with respect to the floor and supported with a foot pedal rear end located directly below the waste compartment being located above a foot pedal front end that is away from the waste compartment and that the foot pedal rear end swings in a vertical direction by using the foot pedal front end as a fulcrum, the foot pedal-type waste flap opening/closing mechanism further comprising a waste flap swing mechanism that engages with the waste flap and is configured to swing the waste flap from the closed position to the opened position, wherein the waste flap swing mechanism comprises an inner arm comprising an engagement portion that is swingably supported inside the chute, and an engaged portion provided in the waste flap, wherein the engagement portion is detachably engaged with the engaged portion and is formed in an open shape in a direction of swing of the waste flap from the closed position to the opened position, and wherein the inner arm is configured to swing by stepping on the foot pedal, and the engagement portion engages with the engaged portion and is configured to swing the waste flap from the closed position to the opened position. a waste compartment adapted to be provided on a floor of the aircraft lavatory unit installed in an aircraft and comprising an opening portion through which a waste container is taken in and out; a chute provided in an upper portion of the waste compartment and comprising a trash feeding opening; and a waste flap swingably supported by the chute between a closed position for closing the trash feeding opening and an opened position for opening the trash feeding opening and biased in a direction of closing the trash feeding opening; a foot pedal adapted to be disposed close to a section on the floor directly below the waste compartment; a foot pedal-type waste flap opening/closing mechanism configured to swing the waste flap from the closed position to the opened position by stepping on the foot pedal, the foot pedal-type waste flap opening/closing mechanism comprising a foot pedal support mechanism that swingably supports the foot pedal between an upper limit position at which the foot pedal is configured to be stepped on and a lower limit position at which the foot pedal is stepped on from the upper limit position and biases the foot pedal allowing the foot pedal to be located at the upper limit position, and the foot pedal support mechanism being configured such that the foot pedal at the upper limit position is inclined with respect to the floor and supported with a foot pedal rear end located directly below the waste compartment being located above a foot pedal front end that is away from the waste compartment and that the foot pedal rear end swings in a vertical direction by using the foot pedal front end as a fulcrum, the foot pedal-type waste flap opening/closing mechanism further comprising a waste flap swing mechanism that engages with the waste flap and is configured to swing the waste flap from the closed position to the opened position, wherein the waste flap swing mechanism comprises an inner arm comprising an engagement portion that is swingably supported inside the chute, and an engaged portion provided in the waste flap, wherein the engagement portion is detachably engaged with the engaged portion and is formed in an open shape in a direction of swing of the waste flap from the closed position to the opened position, and wherein the inner arm is configured to swing by stepping on the foot pedal, and the engagement portion engages with the engaged portion and is configured to swing the waste flap from the closed position to the opened position.