A caulking assisting device has of a fixed frame mounted to a filler coating-supplying device, a rolling part mounted to the fixed frame, a movable frame and an elastic element. The positioning frame has a pair of first limiting recesses and a pair of second limiting recesses. The movable frame is pivoted to the fixed frame and is rotatable, and a tapered roller is pivoted at the end of the movable frame. Meanwhile, the elastic element is disposed on the movable frame, while a positioning protrusion is located at both ends respectively. As a result, the tapered roller can be moved to a use position and a non-use position by the rotation of the movable frame, thereby switching between the rolling part and the tapered roller while in use.