To surely prevent entry of rainwater between a panel peripheral edge and an opening peripheral edge inside a building almost all over the periphery with lower assembling cost.

In this movable panel sealing structure, an opening C formed in a building outer wall B is provided to be closable with a movable panel A which is wholly operable for reciprocating to the outside of a building and a gasket 3 is provided between the panel peripheral edge 1 of the movable panel closing the opening and the opening peripheral edge 2 of the outer wall. On a panel side gasket 3a mounted at the panel peripheral edge, a first protruded piece 16 which can contact the building outer face of the outer wall in the state of closing the opening with the movable panel and a second protruded piece 17 which is located inside of the building beyond the building outer face and protruded toward the opening peripheral edge are formed in series to be mounted at the panel peripheral edge almost all over the periphery.