A protector includes a supporting member mounted on a needle assembly having a needle main body an outer cover member arranged to incline to the needle main body by having an arm axially supported to the supporting member and an inner cover member arranged inside the outer cover member. The outer cover member has a cylindrical body having a needle slit extending in an axial direction for insertion of the needle main body. The inner cover member has an arcuate column, which interlocks with the needle assembly when the outer cover member inclines to insert the needle main body into the needle slit, and rotates by sliding on the inner surface of the cylindrical body. The arcuate column has a circular arc cross-section with an area facing at least the needle slit opened to the cylindrical body at an opened position, the needle slit being covered at a closed position.
