A safety side cover of a syringe is suitable for being sleeved on the syringe including a needle body, and includes a base body and a cover body pivotally connected to the base body. The base body includes a ring-shaped base portion, a pivot portion protruding radially outward from the base portion, and a radial protrusion protruding radially outward from a side of the base portion away from the needle body, and located at the pivot The first stop on one side of the joint. The cover body includes a pivot portion pivotally disposed at the pivot portion, and a first limiting portion extending radially outward from the pivot portion and detachably abutting against the first stop portion, so that The cover body can pivot relative to the base body from an open position revealing the needle body to a closed position covering the needle body, and in the open position, the first limiting portion and the first stop The stoppers interfere with each other and prevent the lid from contacting the syringe.一種注射器的安全側蓋，適用於套設在包括一針體的該注射器，並包含一基座體，及一樞接於該基座體的蓋體。該基座體包括一呈環狀的基部、一自該基部徑向朝外凸設的樞接部，及一自該基部遠離該針體之一側徑向朝外凸設，並位於該樞接部其中一側的第一擋止部。該蓋體包括一樞設於該樞接部的樞軸部，及一自該樞軸部徑向朝外延伸且可分離地靠抵於該第一擋止部的第一限位部，使該蓋體能相對於該基座體自一顯露該針體的開啟位置樞轉至一罩覆該針體的蓋合位置，且在該開啟位置時，該第一限位部與該第一擋止部互相干涉，並使該蓋體不接觸該注射器。
