An ink supply device of a printing machine, said ink supply device comprising a plurality of ink transfer rollers, an ink fountain roller which constitutes an ink fountain and a control device, wherein the plurality of ink transfer rollers are divided in the lengthwise direction of the ink fountain roller which constitutes the ink fountain are arranged adjacent to the ink fountain roller, the respective ink transfer rollers are individually changeable over between a transfer position where the ink transfer roller is brought into contact with the ink fountain roller and a non-transfer position where the ink transfer roller is disposed away from the ink fountain roller, and using the control device, based on a graph value set corresponding to a pattern area of a printed matter, ink is transferred by changing over a position of a required ink transfer roller for every transfer timing at predetermined intervals, and a rotational angle of the ink fountain roller from a position where the ink transfer roller is brought into contact with the ink fountain roller to a position where the ink transfer roller is separated from the ink fountain roller is controlled for every ink transfer roller thus controlling a circumferential length of ink transferred to the ink transfer roller from the ink fountain roller, wherein the graph value is a target value of an ink quantity indicating a quantity of ink having predetermined color to be used for every ink transfer roller, each ink transfer roller is provided with a roller position switching device which is able to change over the position of the ink transfer roller, each switching device is controllable by the control device, characterized in that the control device comprises: a concentration prediction value calculation means which acquires a concentration prediction value when the concentration of ink becomes stable based on concentration of ink measured values of a predetermined number of printed matters; a graph change value calculation means which acquires a graph change value using the concentration prediction value and a concentration target value; and a control graph value calculation means which acquires a control graph value for controlling the rotational angle of the required ink fountain roller based on a preset set graph value and the graph change value, wherein the control device performs at the time of exchanging an original plate, a comparison between a pattern area before exchanging the original plate and a pattern area after the exchange of the original plate with respect to all ink transfer rollers, when the pattern area is increased after the exchange of the original plate, additional ink distribution is performed, when the pattern area is decreased after the exchanging the original plate, an operation of the ink transfer roller is stopped for a fixed time, and assuming that the pattern area before exchanging the original plate is A(%), a retention ink quantity (%) of the ink transfer roller before exchanging the original plate is Y+AZ(%), the pattern area after the exchange of the original plate is B(%), a retention ink quantity(%) after the exchange of the original plate is Y+BZ(%), the following operations are performed corresponding to whether the difference (B-A)Z(%) before arid after the exchange of the original plate takes a positive value or a negative value, whereby Y is the ink retained by the ink transfer roller having a uniform thickness over the whole region ranging from one end to the other end of the ink transfer roller, and whereby Z is a constant indicating the proportion between the thickness of ink and the pattern area, and additional ink distribution is performed Z times in case of (B-A)Z>0, and ink transfer amounting to (A-B)Z/B times is stopped in case of (B-A)Z<0.