A natural ventilation window 1 includes: a framed panel 2 and an opening/closing means 5 for causing the framed panel 2 to open and close an opening portion 4 of a building on the basis of an air current 3. The opening/closing means 5 includes a supporting mechanism 32 for supporting a portion 31 on a top rail 22 side of the framed panel 2 liftably and rotatably about a horizontal axis S 1 in an R1 direction; a supporting mechanism 34 for supporting a portion 33 of the framed panel 2, which is located below the portion 31, movably in a direction A toward the interior or exterior of the building and rotatably about a horizontal axis S2 in an R2 direction; and an engaging member 35 for causing the framed panel 2 to engage a window frame 11 defining the opening portion 4, so as to maintain a state of the opening portion fully closed by the framed panel 2.