To provide a method for precisely detecting and managing the density of ink, including a special color, which is used in printed matter and a device using this method.

In this method, the value of data to be used for managing the color density of printed matter is previously stored in an operation setting part 9 or a data management part 6; and data to be used for color density management are inputted or read based on the stored data and stored in a control part 5. Further, a mark 12 for density detection put on the printed matter is detected in a timely manner using a position detecting device 3; the density of the mark 12 put on the printed matter is detected as a density signal using a sensor 1 for detecting the density of the special color; the density signal is processed by amplification and A/D conversion using an input signal processing part 4; and the signal-processed density signal is compared with the density management data stored in the control part 5 and an arithmetic operation is performed on the comparison results. After these procedures, it is judged whether the density of the special color of the printed matter has passed or failed through the comparison/arithmetic operation; and the density of the special color of the printed matter is managed based on the results of outputted information to a display part 8 regarding the judgement results and printed matter quality management.