Abstract: A paint sprayer includes a threaded hole defined in a barrel thereof and a connection member is threadedly engaged with the threaded hole. A passage defined through the connection member and shares a common axis with the threaded hole in the sprayer. An eccentric hole is defined in a top of the connection member and an annular groove is defined in an inner periphery of the eccentric hole. An inner diameter of the annular groove is larger than an inner diameter of the eccentric hole. An insertion piece has a first end fixed to a cup and a flange eccentrically extends outward from an outer periphery of the insertion piece. A second end of the insertion piece is rotatably inserted in the connection member via the eccentric hole and the flange is rotatably engaged with the annular groove. The cup can be quickly disengaged from or connected to the sprayer by rotating the cup less than one revolution.