Even if an error occurred in a result of the detection by an optical detecting mechanism for optically detecting whether or not a remaining amount of ink in an ink tank is equal to or less than a predetermined amount, a correct situation of the remaining ink amount in the ink tank can be detected. A detecting method has a first discriminating step of discriminating whether or not a remaining ink amount in the ink tank is equal to or less than a predetermined amount by using an optical sensor and a second discriminating step of discriminating whether or not the remaining ink amount in the ink tank is equal to or less than the predetermined amount on the basis of information regarding an amount of ink consumed in the ink tank. If the absence of ink is determined in either the first or second discriminating step, information showing the absence of ink is notified.