A connection device for a cable management arm and a slide assembly includes a connection member, an engaging member and an insertion piece. The connection member is fixedly connected to the cable management arm and includes a passage and a window. The engaging member is fixedly connected to the connection member and has a resilient arm and an engaging portion. The resilient arm is located corresponding to the window. The insertion piece is fixedly connected to the slide assembly and has two insertion arms. One of the insertion arms has a contact section located corresponding to the engaging portion. When the insertion piece is inserted into the passage, the engaging portion of the engaging member contacts the contact section of the insertion arm to position the insertion piece to the connection member.