Abstract: An outer casing having a waterproof function for an electronic apparatus includes a casing body and a side cover waterproof mechanism. The side cover waterproof mechanism includes a cover body and a limit rib. The cover body includes a plastic layer and a silica gel layer integrally disposed under the plastic layer. The plastic layer is embedded an outer interface of the casing body. The silica gel layer is embedded in an inner interface of the casing body. The limit rib is slidably disposed in an accommodation trough. Between upper and lower casing bodies of the casing body is provided with a silica gel seal ring for sealing. Thus, between the upper and lower casing bodies of the electronic apparatus and between the interfaces of the casing bodies are provided with a waterproof mechanism, respectively, to enhance the waterproof capability of the electronic apparatus.