A toilet seat structure for an aircraft lavatory unit, comprising: a toilet body including a bowl portion; a support portion configured to support the toilet body above a floor; a shroud including: a peripheral wall portion configured to cover a periphery of the toilet body and the support portion and a flange having an annular plate shape and being placed on an upper end outer circumferential plate portion of the bowl portion; a toilet seat having an annular shape with a width and being placed on the flange; a shroud cushion block being attached on a lower surface of the flange facing the upper end outer circumference plate portion while securing an air communication passageway; and a toilet seat cushion block being attached on a lower surface of the toilet seat facing the flange, wherein the air communication passageway is configured to communicate with an inside and an outside of the bowl portion; the toilet seat cushion block being attached while securing an air communication passageway configured to communicate with the inside and the outside of the bowl portion; characterized in that the toilet seat cushion block has a band-like shape extending along a circumferential direction of the lower surface of the toilet seat and is positioned in substantially an entire area of the circumferential direction of the lower surface of the toilet seat while securing the air communication passageway at each of a plurality of sections at an interval in an extension direction of the toilet seat cushion block, and in a state in which a section of the toilet seat directly above the air communication passageway is stepped on with a foot, in a plan view, the toilet seat cushion block is positioned inward of a contour of the foot. a toilet body including a bowl portion; a support portion configured to support the toilet body above a floor; a shroud including: a peripheral wall portion configured to cover a periphery of the toilet body and the support portion and a flange having an annular plate shape and being placed on an upper end outer circumferential plate portion of the bowl portion; a peripheral wall portion configured to cover a periphery of the toilet body and the support portion and a flange having an annular plate shape and being placed on an upper end outer circumferential plate portion of the bowl portion; a toilet seat having an annular shape with a width and being placed on the flange; a shroud cushion block being attached on a lower surface of the flange facing the upper end outer circumference plate portion while securing an air communication passageway; and a toilet seat cushion block being attached on a lower surface of the toilet seat facing the flange, the air communication passageway is configured to communicate with an inside and an outside of the bowl portion; the toilet seat cushion block being attached while securing an air communication passageway configured to communicate with the inside and the outside of the bowl portion; characterized in that the toilet seat cushion block has a band-like shape extending along a circumferential direction of the lower surface of the toilet seat and is positioned in substantially an entire area of the circumferential direction of the lower surface of the toilet seat while securing the air communication passageway at each of a plurality of sections at an interval in an extension direction of the toilet seat cushion block, and in a state in which a section of the toilet seat directly above the air communication passageway is stepped on with a foot, in a plan view, the toilet seat cushion block is positioned inward of a contour of the foot.