Abstract: In a base hinge device comprising a resin-made base hinge and a resin-made arm hinge rotatably engaging the resin-made base hinge through a rotary shaft; one of the resin-made base hinge and resin-made arm hinge having the rotary shaft, while the other having a rotary shaft bearing for pivotally supporting the rotary shaft; a biasing member arranged on the rotary shaft side and a slider arranged on the rotary shaft bearing side being interposed between the rotary shaft and rotary shaft bearing; the slider has a projection on an outer periphery thereof, the projection being adapted to be pressed at an inner periphery of the rotary shaft bearing toward the biasing member and displaced so as to be pushed in.