1. A simulating system comprising: a data retrieving device which time-sequentially retrieves a control value which is outputted from a control system in an image forming apparatus to a controlled system and an input value which is inputted from said controlled system to said control system as a control result of said controlled system by said control value; a data storing device which stores a time-series data group including a plurality of said control values which have time-sequentially been retrieved by said data retrieving device and the input values corresponding to said control values; and a simulating device which simulates the control result of said controlled system of said image forming apparatus corresponding to the control value which is outputted to said controlled system in accordance with an algorithm to identify the operation of said controlled system of said image forming apparatus, wherein a correlation between each of the control values and the input value corresponding to each of said control values included in the time-series data group stored in said data storing device has been implemented in said algorithm of said simulating device.