A protector includes a protector body, a lid member, and an engagement mechanism. The lid member has a ceiling and a protrusion. When a first wiring member and a second wiring member are accommodated in an accommodating space in a non-regular arrangement in which a peripheral surface of the first wiring member contacts a bottom and a peripheral surface of the second wiring member contacts the peripheral surface of the first wiring member, the peripheral surface of the second wiring member contacts the protrusion on the way of the transition of the engagement mechanism from a non-engagement state to an engagement state. When accommodated in a regular arrangement, the engagement mechanism transitions from the non-engagement state to the engagement state.