PURPOSE: To facilitate positioning without needing a tool when a pulley is mounted by providing a lock part through which a pulley cover having a pulley covered therewith and a bracket are fitted in each other.

CONSTITUTION: A pulley cover 1 made of plastic is arranged to the pulley 12 of an oil pump 11 and a mounting part 2 in which a hole part 28 is formed is arranged on the bracket 13 side on the one side in a longitudinal direction, and a bolt 14 is joined in a screwed-in state with the screw hole 13a of the bracket 13. A key part 3 in a T-shape in cross section having a press part 3b is formed on the bracket 13 side on the other end side. The key part 13 and a support plate 15 having the key part 3 and an insertion groove part 15a are arranged on the pulley 12 side of the bracket 13. The key part 3 is inserted in the groove part 15a and locked thereto, and the bolt 14 is inserted in the hole part 2a and joined in a screwed-in state with the screw hole 13a, and this way facilitates mounting of the pulley cover 1 on the bracket 13. This constitution simplifies mounting of the pulley cover.