A fixing bracket for a window frame is provided to improve stability and facilitate the finishing work for the window frame by reducing a gap between a window frame and a wall. A fixing bracket for a window frame comprises a fixation member(10), a movable member(12) and a position fixing bolt(48). The fixation member(10) includes a vertical unit(14) and a horizontal unit(16), which are perpendicular to each other. Bending struts(27,27') support the horizontal unit(16) at two opposite sides of the vertical unit(14). The movable member(12) includes a plate unit(30), which corresponds to the horizontal unit(16) of the fixation member(10), and bending sidewalls(32,32'). The position fixing bolt(48) includes an outer spiral section(44), which is screw-coupled with a guide hole(26) in the fixation member(10).