A lens cap includes a ring detachably mounted onto a lens of an optical apparatus and a pair of linkage sets pivotally connected to the ring, wherein the two linkage sets are diametrically corresponding to each other and respectively connected to a covering structure. A sleeve is longitudinally and slidably sleeved on the ring and the covering structure is connected to sleeve. As a result, the covering structure selectively opens/closes the sleeve when the sleeve is reciprocally moved relative to the ring. The covering structure and the sleeve are used as a lens cap when the covering structure closing the sleeve, and used as a lens hood when the covering structure is opened.