A head guard structure for a forklift, comprising: a pair of right and left front pillars (51, 51) mounted to a front of a vehicle body of a forklift and spaced from each other in a vehicle width direction; a pair of right and left rear pillars (52, 52) mounted to a rear of the vehicle body and spaced from each other in the vehicle width direction; a pair of right and left vertical frames (55, 55) connecting upper ends of the front pillars and upper ends of the rear pillars in a vehicle front-rear direction; a front lateral frame connecting the upper ends of the pair of right and left front pillars (51, 51) in the vehicle width direction; a top board disposed over the pair of right and left vertical frames (55, 55) via flanges at opposite ends of the top board in the vehicle width direction disposed on upper surfaces of the vertical frames (55, 55), so as to extend from rear ends of the vertical frames toward front of the vehicle, the top board including a front edge disposed at a center of the vertical frames in a front-rear direction and a front flange surface formed continuously from the front edge and bended downward; and a plurality of bar members each including a first end fixed to the front lateral frame and a second end fixed to the front flange surface, the bar members being arranged at intervals in the vehicle width direction, characterised in that a gusset of a substantially L shape of a thick plate formed by a first arm disposed along the inner side of the upper end of the rear pillars and a second arm disposed along the inner side of the rear end of the vertical frames is welded to a joint portion between the vertical frame and the rear pillar, such that the gusset is welded to the vertical frame 55) and to the rear pillar over the entire periphery of the gusset continuously, wherein the ends of the first arm and the second arm of the L shape are each formed into a semi-circle shape. a pair of right and left front pillars (51, 51) mounted to a front of a vehicle body of a forklift and spaced from each other in a vehicle width direction; a pair of right and left rear pillars (52, 52) mounted to a rear of the vehicle body and spaced from each other in the vehicle width direction; a pair of right and left vertical frames (55, 55) connecting upper ends of the front pillars and upper ends of the rear pillars in a vehicle front-rear direction; a front lateral frame connecting the upper ends of the pair of right and left front pillars (51, 51) in the vehicle width direction; a top board disposed over the pair of right and left vertical frames (55, 55) via flanges at opposite ends of the top board in the vehicle width direction disposed on upper surfaces of the vertical frames (55, 55), so as to extend from rear ends of the vertical frames toward front of the vehicle, the top board including a front edge disposed at a center of the vertical frames in a front-rear direction and a front flange surface formed continuously from the front edge and bended downward; and a plurality of bar members each including a first end fixed to the front lateral frame and a second end fixed to the front flange surface, the bar members being arranged at intervals in the vehicle width direction, characterised in that a gusset of a substantially L shape of a thick plate formed by a first arm disposed along the inner side of the upper end of the rear pillars and a second arm disposed along the inner side of the rear end of the vertical frames is welded to a joint portion between the vertical frame and the rear pillar, such that the gusset is welded to the vertical frame 55) and to the rear pillar over the entire periphery of the gusset continuously, wherein the ends of the first arm and the second arm of the L shape are each formed into a semi-circle shape.