A window comprising an opening frame, a fixed sash fixed to the opening frame and a movable sash, wherein the opening frame has a top frame member, a bottom frame member, a first vertical frame member and a second vertical frame member, wherein the fixed sash has a top rail, a bottom rail, a head end stile member and a tail end stile member, bonded to respective peripheral ends of a fixed multi-layered planar material having a rectangular outer shape, wherein the movable sash has a top rail, a bottom rail, a head end stile member and a tail end stile member, bonded to respective peripheral ends of a movable multi-layered planar material having a rectangular outer shape, wherein the opening frame further comprises a guide rail and a slide housing groove on the bottom frame member, and a guide groove and a housing portion on the top frame member, wherein the guide groove is a depression formed on the lower surfaces of the top frame member along the longitudinal direction of the top frame member, and has a pair of top guide surfaces formed along a sash width direction on a thickness direction surface of the frame member wherein the housing portion is formed in a thickness direction surface of the guide groove provided on the frame member, wherein the window further includes a guide member provided on a thickness direction surface of the top rail serving as an end face of the movable sash, the guide groove facing the top rail, and the movable sash is provided so as to be slidable along the longitudinal direction of the top rail in a state in which the guide member abuts on the respective guide surfaces, the window further comprising: a slide member that is provided on the top rail so as to slide along the longitudinal direction of the top rail; and an operating handle that is provided on the movable sash and, when operated, slides the slide member relative to the top rail, wherein the guide member comprises: a guide arm that is provided so as to be rotatable relative to the top rail on a support shaft orthogonal to the thickness direction surface of the top rail and so as to be movable along the thickness direction; guide rollers provided at both ends of the guide arm; and a regulating member (66, 67, 68, 69) that regulates rotation of the guide arm relative to the top rail, when the guide arm is held in the projecting attitude relative to the top rail by the regulating member (66, 67, 68, 69), circumferential surfaces of the guide rollers project from the respective thickness-direction-facing surfaces of the movable sash, and the guide arm abuts on the guide surfaces via the guide rollers, whereas when the guide arm is in the retracted attitude, the guide arm and the circumferential surfaces of the guide rollers are disposed within the width along the thickness direction of the movable sash, wherein the guide arm and the guide rollers are disposed in the retracted attitude in the housing portion, and wherein the guide arm and the guide rollers are not accomodatable in the housing portion in the projecting attitude, a shift mechanism is interposed between the top rail and the guide member, the shift mechanism moving the guide member along the thickness direction relative to the top rail according to the slide of the slide member. a slide member that is provided on the top rail so as to slide along the longitudinal direction of the top rail; and an operating handle that is provided on the movable sash and, when operated, slides the slide member relative to the top rail, wherein the guide member comprises: a guide arm that is provided so as to be rotatable relative to the top rail on a support shaft orthogonal to the thickness direction surface of the top rail and so as to be movable along the thickness direction; guide rollers provided at both ends of the guide arm; and a regulating member (66, 67, 68, 69) that regulates rotation of the guide arm relative to the top rail, a guide arm that is provided so as to be rotatable relative to the top rail on a support shaft orthogonal to the thickness direction surface of the top rail and so as to be movable along the thickness direction; guide rollers provided at both ends of the guide arm; and a regulating member (66, 67, 68, 69) that regulates rotation of the guide arm relative to the top rail, when the guide arm is held in the projecting attitude relative to the top rail by the regulating member (66, 67, 68, 69), circumferential surfaces of the guide rollers project from the respective thickness-direction-facing surfaces of the movable sash, and the guide arm abuts on the guide surfaces via the guide rollers, whereas when the guide arm is in the retracted attitude, the guide arm and the circumferential surfaces of the guide rollers are disposed within the width along the thickness direction of the movable sash, wherein the guide arm and the guide rollers are disposed in the retracted attitude in the housing portion, and wherein the guide arm and the guide rollers are not accomodatable in the housing portion in the projecting attitude, a shift mechanism is interposed between the top rail and the guide member, the shift mechanism moving the guide member along the thickness direction relative to the top rail according to the slide of the slide member.