An adjusting device for tightening or loosing laces and straps includes a base, an actuating member and a knob. When a user rotates the knob clockwise, the adjusting device is tightening a flexible strap of the clothing or a lace of the footwear. However, when a user rotates the knob counterclockwise, the adjusting device is loosing a flexible strap of the clothing or a lace of the footwear. The knob never moves up and down along the axis during the operation for tightening or loosing the flexible strap or the lace.