A male connector comprises: a holder, attached rotatably to the outer peripheral surface of a plug main unit portion, having male threads formed on the outer peripheral surface thereof and having sliding grooves formed at specific intervals at the rearward side on the outer peripheral surface; and a knob portion, formed integrally with engaging protruding portions that have engaging hooks on the tip end sides thereof and that sliding in the sliding grooves, where the knob portion is attached so as to be able to rotate together with the holder.