To provide a protective cover of a steering column which can prevent a steering lock device from being unlocked by being removed from the steering column, and whose moldability is excellent, and a mounting structure of the protective cover of the steering column.

The protective cover of the steering column 1 is mounted on the steering column 1 to cover the steering lock device 2 of the steering column 1. A first cover part 10 and a second cover part 20 are formed by welding connection, and fastened to the steering column 1 with a bolt B inserted into a fastening fixture hole H1 of the first cover part 10. A protective flange 29 covering at least a vehicle rear side Rr at the end in a shaft direction of the bolt B is formed in the second cover part 20.