An aircraft gas turbine comprising: a rotor (21,91) configured to rotate around an axis (Am); a rotor blade having a rotor blade main body extending radially outward from the rotor (21,91), a rotor blade shroud provided at a tip of the rotor blade main body, and a fin (43,43B) projecting from an outer peripheral surface of the rotor blade shroud; a casing (22,92) surrounding the rotor (21,91) and the rotor blade from an outer periphery side and forming a gap with the fin (43,43B); a stationary blade having a stationary blade shroud and a stationary blade main body extending radially inward from the stationary blade shroud, the stationary blade shroud fixed to the casing (22,92) on a downstream side of the rotor blade such that a cavity (Ct) is formed by at least the stationary blade shroud, the rotor blade shroud and the fin (43,43B); and a guide member (53;153) provided in the cavity (Ct) and extending inward from a radial outer side (Dro), an inner-side end part (53a;153a) of the guide member (53;153) on a radial inner side (Dri) facing the outer peripheral surface of the rotor blade shroud with a gap therebetween, wherein the outer peripheral surface of the rotor blade shroud facing the inner-side end part (53a;153a) of the guide member (53;153) is formed in parallel with the axis (Am), characterized in that the guide member (53;153) is provided with an inclined portion (54;154) which is inclined radially outward from the inner-side end part (53a;153a) of the guide member (53;153) so as to approach the stationary blade in a downstream direction in which the axis (Am) extends, and wherein the inner-side end part (53a;153a) of the guide member (53;153) is disposed closer to the axis (Am) in the radial direction than an inner peripheral surface of the stationary blade shroud. a rotor (21,91) configured to rotate around an axis (Am); a rotor blade having a rotor blade main body extending radially outward from the rotor (21,91), a rotor blade shroud provided at a tip of the rotor blade main body, and a fin (43,43B) projecting from an outer peripheral surface of the rotor blade shroud; a casing (22,92) surrounding the rotor (21,91) and the rotor blade from an outer periphery side and forming a gap with the fin (43,43B); a stationary blade having a stationary blade shroud and a stationary blade main body extending radially inward from the stationary blade shroud, the stationary blade shroud fixed to the casing (22,92) on a downstream side of the rotor blade such that a cavity (Ct) is formed by at least the stationary blade shroud, the rotor blade shroud and the fin (43,43B); and a guide member (53;153) provided in the cavity (Ct) and extending inward from a radial outer side (Dro), an inner-side end part (53a;153a) of the guide member (53;153) on a radial inner side (Dri) facing the outer peripheral surface of the rotor blade shroud with a gap therebetween, wherein the outer peripheral surface of the rotor blade shroud facing the inner-side end part (53a;153a) of the guide member (53;153) is formed in parallel with the axis (Am), characterized in that the guide member (53;153) is provided with an inclined portion (54;154) which is inclined radially outward from the inner-side end part (53a;153a) of the guide member (53;153) so as to approach the stationary blade in a downstream direction in which the axis (Am) extends, and wherein the inner-side end part (53a;153a) of the guide member (53;153) is disposed closer to the axis (Am) in the radial direction than an inner peripheral surface of the stationary blade shroud.