A closed male luer includes a first connector having an upper end portion defining an axial recess, an inner circumferential slide track and several first ratchet teeth and a second connector having lower end portion received in the axial recess of the first connector, having several second ratchet teeth selectively meshed with the first ratchet teeth such that rotation of the first connector in a first direction drives the second connector to rotate simultaneously in the first direction, wherein, after an upper end portion of the second connector is connected with a second member, rotation of the first connector in the first direction or rotation of the second connector in a second direction opposite to the first direction can break up the second ratchet teeth into pieces by the first ratchet teeth, hence permitting the second connector to rotate freely in 360° relative to the first connector.
