To make an adjustment so as to accurately open at 180 degrees when fully opening two slats of a hinge for a folding door at 180 degrees.

This hinge of the folding door has a positioning member 7 having fixing recessed parts 26, 27, and 28 in three states of a full opening state, a half opening state, and a full closure state with a rotary shaft as the center on one slat 4; has a pressing member 8 for fixing a position by being pressed in the respective fixing recessed parts 26, 27, and 28 in the other slat 5; is characterized in that the positioning member 7 has an adjusting member 23 projecting in the fixing recessed part 26 in the full opening state by rotating with the rotary shaft as a fulcrum, and an adjusting screw 32 rotated by acting on the adjusting member 23; and a full opening angle of the two slats 4 and 5 can be adjusted by adjusting the length projecting in the fixing recessed part 26 in the full opening state of the adjusting member 23 by adjusting this adjusting screw 32.