A main frame supports a printer head. A first movable frame supports a platen and a first paper feeding roller, and is pivotally connected to one end of the main frame via a first pivot shaft to permit itself to be opened or closed relative to the main frame. A second movable frame supports a second paper feeding roller, and is pivotally connected to the other end of the main frame via a second pivot shaft to permit itself to be opened or closed relative to the main frame. When the first movable frame and the second movable frame are closed relative to the main frame, the printer head is opposite to the platen to form a printing position; and the first paper feeding roller is tangent to the second paper feeding roller.