A pulley apparatus for a slide door opening and closing mechanism for opening and closing a slide door disposed on one side of a vehicle, the pulley apparatus changing a pulling direction of a cable (17, 18) which pulls the slide door, the pulley apparatus comprising: a pulley case disposable on one side of a vehicle body panel forming part of the vehicle; a pulley rotatably disposed in the pulley case, the pulley having a pulley groove into which the cable is guided; and a cable guide disposed in the pulley case, the cable guide guiding the cable to one side of the vehicle body panel from the other side of the vehicle body panel, the cable guide being in sliding contact with the cable and curving the cable along the vehicle body panel to direct the cable to the pulley, the pulley case has a case body fixable to the vehicle body panel and a case cover for closely covering up the case body, the case body and the case cover are respectively formed with fitting holes (43, 55) in which ends of a pulley shaft for rotatably supporting the pulley are respectively fitted, the pulley being disposed in the pulley case such that the axial direction of the pulley matches the thickness direction of the vehicle body panel, characterized in that: Z engagement claws are formed on a peripheral edge of the case body, each projecting from a surface of the case body in a thickness direction of the case body, and each having a given height, engagement projections are formed on an outer periphery of an outer peripheral wall of the case cover, each projecting outward from the outer peripheral wall to have a minute height, the case cover is fitted to the case body by the engagement claws and the engagement projections, the case cover has a pair of fitting portions which extend in respective directions opposite to each other along the vehicle body panel, and are fixable to and abut the vehicle body panel with respective fastening bolts, the cable guide being disposed closer to the pulley than the fitting portions of the pulley case along the vehicle body panel. a pulley case disposable on one side of a vehicle body panel forming part of the vehicle; a pulley rotatably disposed in the pulley case, the pulley having a pulley groove into which the cable is guided; and a cable guide disposed in the pulley case, the cable guide guiding the cable to one side of the vehicle body panel from the other side of the vehicle body panel, the cable guide being in sliding contact with the cable and curving the cable along the vehicle body panel to direct the cable to the pulley, engagement claws are formed on a peripheral edge of the case body, each projecting from a surface of the case body in a thickness direction of the case body, and each having a given height, engagement projections are formed on an outer periphery of an outer peripheral wall of the case cover, each projecting outward from the outer peripheral wall to have a minute height, the case cover is fitted to the case body by the engagement claws and the engagement projections, the case cover has a pair of fitting portions which extend in respective directions opposite to each other along the vehicle body panel, and are fixable to and abut the vehicle body panel with respective fastening bolts, the cable guide being disposed closer to the pulley than the fitting portions of the pulley case along the vehicle body panel.