A wire housing protector in which a locking mechanism includes an elastic projecting piece provided in a lid with an engagement protrusion on an outer surface of its leading end, and an elastic projecting piece insertion portion that is provided in a side wall of the protector body, and includes an engagement portion that engages with the engagement protrusion, contact surfaces include first engagement surfaces that each extend from the side wall side of the protector body toward a side to which the engagement protrusion protrudes, second engagement surfaces that extend from end portions of the first engagement surfaces toward the lid side, and third engagement surfaces that extend from end portions of the second engagement surfaces toward the side to which the engagement protrusion protrudes.