A T-joint includes a pipe body and a switch. The pipe body includes an inlet opening, a first outlet opening, a second outlet opening and a switch accommodating space communicating with each other. The switch is positioned into the switch accommodating space of the pipe body, and includes a pressed member and an outlet-selecting member. The pressed member and the outlet-selecting member are connected to each other. By pressing either a first pressed portion or a second pressed portion of the pressed member, the isolating member of the switch could be positioned to lead the inlet opening to communicate with a corresponding one of the first outlet opening and the second outlet opening.