PROBLEM TO BE SOLVED: To enhance reliability in attaching a needle to an injection syringe.SOLUTION: A breakage resistant engaging structure is a structure for engaging a needle 200 and a cylindrical cover 100 for the needle, the needle 200 being configured to be screwed in a syringe 300 with a flange 211 at an end of a needle base 201, and the cover 100 being configured to be capped on the needle 200 integrally to the needle base 201. The needle base 201 is provided with projections (needle base ribs 240) on the outer periphery thereof, and the cover 100 is provided with projections (longitudinal ribs 110) on the inner periphery thereof, the needle base ribs 240 and the longitudinal ribs 110 both extending longitudinally, being disposed in rotational symmetry in the same number, and being configured to interfere with each other if rotated. The cover 100 is provided with slant faces 111 on the inner periphery, the slant face 111 rasing from a point ahead of the rotational direction when the cover 100 is rotated clockwise as viewed to a capping hole 101.
