A sunshade device disposable inside a rear package tray as part of a window peripheral member and configured to shield a window with a shade drawn out through a slit formed in said rear package tray, the sunshade device comprising: a windup device including a windup shaft supported so as to rotate about its axis; said shade including a short side edge and a long side edge opposed to each other and configured to be drawn from and housed in said windup device through said slit, said long side edge being attached to said windup shaft; a stay attached to said short side edge of said shade; a cover body configured to switch to move between a closing state of partially covering said slit and an opening state of opening said slit and in said closing state, configured to cover said slit together with said stay in the state in which said shade is housed; and an associating mechanism operating said cover body to switch between said closing state and said opening state with the movement of said stay such that said cover body moves into said closing state in the state in which said shade is housed, characterized in that: said associating mechanism includes: a slide member provided so as to be moved along a drawing direction and a housing direction of said shade by a movement of said stay on a moving track; a slide biasing member biasing said slide member toward said drawing direction of said shade; and a transmission mechanism operating said cover body to switch between said closing state and said opening state, in association with the movement of said slide member. a windup device including a windup shaft supported so as to rotate about its axis; said shade including a short side edge and a long side edge opposed to each other and configured to be drawn from and housed in said windup device through said slit, said long side edge being attached to said windup shaft; a stay attached to said short side edge of said shade; a cover body configured to switch to move between a closing state of partially covering said slit and an opening state of opening said slit and in said closing state, configured to cover said slit together with said stay in the state in which said shade is housed; and an associating mechanism operating said cover body to switch between said closing state and said opening state with the movement of said stay such that said cover body moves into said closing state in the state in which said shade is housed, characterized in that: said associating mechanism includes: a slide member provided so as to be moved along a drawing direction and a housing direction of said shade by a movement of said stay on a moving track; a slide biasing member biasing said slide member toward said drawing direction of said shade; and a transmission mechanism operating said cover body to switch between said closing state and said opening state, in association with the movement of said slide member. a slide member provided so as to be moved along a drawing direction and a housing direction of said shade by a movement of said stay on a moving track; a slide biasing member biasing said slide member toward said drawing direction of said shade; and a transmission mechanism operating said cover body to switch between said closing state and said opening state, in association with the movement of said slide member.