A waste bin device of an aircraft lavatory unit is provided. A chute, waste flap, and waste container are formed from a material having fire resistance performance. A fire spreading prevention space that prevents fire from spreading to the outside of a waste bin device main body due to a flame occurring when inserted waste catches fire is formed inside the waste bin device main body at a storing position of the waste container positioned with regard to a lower portion of the chute. A maintaining portion maintains the waste container at a storing position. The maintaining portion includes a first maintaining portion that maintains from a vertical direction a condition where an upper portion of the waste container and lower portion of the chute are aligned, and a second maintaining portion that maintains the condition from a direction orthogonal to the vertical direction, at the storing position.