An aircraft water tank comprising a tank installation attachment portion provided on a cylindrical body portion of a tank body, the tank installation attachment portion comprising: a base portion that includes a plurality of prepregs being band-like and layered on an outer circumferential surface of the body portion in a radial direction of the body portion, and that extends in a circumferential direction of the outer circumferential surface; a flange that is formed by folding, from the base portion and outward of the body portion in the radial direction, the plurality of prepregs layered and that extends along an extension direction of the base portion; and an attachment plate portion provided on at least one section in an extension direction of the flange, the attachment plate portion including an attachment plate portion prepreg that includes the plurality of prepregs projecting outward from the flange in the radial direction of the body portion while extending along the extension direction of the base portion, a metal plate housed in a housing space inside the attachment plate portion prepreg, and an attachment hole formed to extend through the attachment plate portion prepreg and the metal plate in a direction parallel to an axial direction of the body portion, the metal plate having a length along a circumferential direction of the body portion and a thickness along the direction parallel to the axial direction of the body portion, the attachment hole being formed in an intermediate portion of the metal plate in a longitudinal direction, a thickness of the intermediate portion of the metal plate in the longitudinal direction having a dimension larger than a dimension of a thickness of each of both side portions of the metal plate in the longitudinal direction, and a number of prepregs located on both side portions of the metal plate in the longitudinal direction and outward of both surfaces of the metal plate in a thickness direction being larger than a number of prepregs located in the intermediate portion of the metal plate in the longitudinal direction and outward of both surfaces of the metal plate in the thickness direction. a base portion that includes a plurality of prepregs being band-like and layered on an outer circumferential surface of the body portion in a radial direction of the body portion, and that extends in a circumferential direction of the outer circumferential surface; a flange that is formed by folding, from the base portion and outward of the body portion in the radial direction, the plurality of prepregs layered and that extends along an extension direction of the base portion; and an attachment plate portion provided on at least one section in an extension direction of the flange, the attachment plate portion including an attachment plate portion prepreg that includes the plurality of prepregs projecting outward from the flange in the radial direction of the body portion while extending along the extension direction of the base portion, a metal plate housed in a housing space inside the attachment plate portion prepreg, and an attachment hole formed to extend through the attachment plate portion prepreg and the metal plate in a direction parallel to an axial direction of the body portion, the metal plate having a length along a circumferential direction of the body portion and a thickness along the direction parallel to the axial direction of the body portion, the attachment hole being formed in an intermediate portion of the metal plate in a longitudinal direction, a thickness of the intermediate portion of the metal plate in the longitudinal direction having a dimension larger than a dimension of a thickness of each of both side portions of the metal plate in the longitudinal direction, and a number of prepregs located on both side portions of the metal plate in the longitudinal direction and outward of both surfaces of the metal plate in a thickness direction being larger than a number of prepregs located in the intermediate portion of the metal plate in the longitudinal direction and outward of both surfaces of the metal plate in the thickness direction. the attachment plate portion including an attachment plate portion prepreg that includes the plurality of prepregs projecting outward from the flange in the radial direction of the body portion while extending along the extension direction of the base portion, a metal plate housed in a housing space inside the attachment plate portion prepreg, and an attachment hole formed to extend through the attachment plate portion prepreg and the metal plate in a direction parallel to an axial direction of the body portion, the metal plate having a length along a circumferential direction of the body portion and a thickness along the direction parallel to the axial direction of the body portion, the attachment hole being formed in an intermediate portion of the metal plate in a longitudinal direction, a thickness of the intermediate portion of the metal plate in the longitudinal direction having a dimension larger than a dimension of a thickness of each of both side portions of the metal plate in the longitudinal direction, and a number of prepregs located on both side portions of the metal plate in the longitudinal direction and outward of both surfaces of the metal plate in a thickness direction being larger than a number of prepregs located in the intermediate portion of the metal plate in the longitudinal direction and outward of both surfaces of the metal plate in the thickness direction.