A vane (40;40a;40b;40f) that is to be disposed upstream in an axial direction (Da), in which an axis (Ar) of a turbine rotor rotatable about the axis (Ar) extends, from a blade of the turbine rotor, the vane (40;40a;40b;40f) comprising: a vane body configured to extend in a radial direction (Dr) with respect to the axis (Ar) and having a width (Ww) in a circumferential direction (Dc); an outer shroud formed at a radially outer side of the vane body; an inner shroud (61;61a) formed at a radially inner side of the vane body and configured to form, in a mounted state, a combustion gas flow path through which a combustion gas can flow between the outer shroud and the inner shroud (61;61a); and a retainer (91;91a) protruding from the inner shroud (61;61a) to the radially inner side and extending in the circumferential direction (Dc) centering on the axis (Ar) at a position between an upstream edge of the inner shroud (61;61a) in the axial direction (Da) and a downstream edge of the inner shroud (61;61a) in the axial direction (Da), wherein the retainer (91;91a) is formed with an opening (92;92a) that passes through the retainer (91;91a) in the axial direction (Da) and defines a space through which air can flow, characterized in that the opening (92;92a) formed in the retainer (91;91a) is configured such that air can flow therethrough in operation in the mounted state, the opening (92;92a) is formed in a rectangular shape that has a width (Wo) in the circumferential direction (Dc) and the inner circumferential surfaces defining the opening (92;92a) include a first inner circumferential surface facing one side of the circumferential direction (Dc), a second inner circumferential surface facing the other side of the circumferential direction (Dc), a third inner circumferential surface facing the radially inner side in the radial direction (Dr), and a fourth inner circumferential surface facing the radially outer side in the radial direction (Dr), and the width (Wo) of the opening (92;92a) in the circumferential direction (Dc) is wider than the width (Ww) of the vane body in the circumferential direction (Dc) at a radially inner end of the vane body at a position of the retainer (91;91a) in the axial direction (Da). a vane body configured to extend in a radial direction (Dr) with respect to the axis (Ar) and having a width (Ww) in a circumferential direction (Dc); an outer shroud formed at a radially outer side of the vane body; an inner shroud (61;61a) formed at a radially inner side of the vane body and configured to form, in a mounted state, a combustion gas flow path through which a combustion gas can flow between the outer shroud and the inner shroud (61;61a); and a retainer (91;91a) protruding from the inner shroud (61;61a) to the radially inner side and extending in the circumferential direction (Dc) centering on the axis (Ar) at a position between an upstream edge of the inner shroud (61;61a) in the axial direction (Da) and a downstream edge of the inner shroud (61;61a) in the axial direction (Da), wherein the retainer (91;91a) is formed with an opening (92;92a) that passes through the retainer (91;91a) in the axial direction (Da) and defines a space through which air can flow, characterized in that the opening (92;92a) formed in the retainer (91;91a) is configured such that air can flow therethrough in operation in the mounted state, the opening (92;92a) is formed in a rectangular shape that has a width (Wo) in the circumferential direction (Dc) and the inner circumferential surfaces defining the opening (92;92a) include a first inner circumferential surface facing one side of the circumferential direction (Dc), a second inner circumferential surface facing the other side of the circumferential direction (Dc), a third inner circumferential surface facing the radially inner side in the radial direction (Dr), and a fourth inner circumferential surface facing the radially outer side in the radial direction (Dr), and the width (Wo) of the opening (92;92a) in the circumferential direction (Dc) is wider than the width (Ww) of the vane body in the circumferential direction (Dc) at a radially inner end of the vane body at a position of the retainer (91;91a) in the axial direction (Da).