To perform data gathering accurate for the time by adding the time to gathered data on a controller side.

A controller 102 for gathering and holding trend data and a data base device 101 for gathering the information from the controller 102 at every fixed cycle and preserving it are connected through a LAN 103. The data base device 101 is provided with a clock 104 to be the base of time information and a storage device 105 for storing gathered state information. Based on the respective kinds of definition information 106, the controller 102 gathers the trend data from a device connected to a system inside the system at every fixed cycle by its own clock 104 and stores the gathered data in its own memory. Simultaneously, gathering time information and status information are added and they are transmitted to the data base device 101. The data base device 101 receives (gathers) the trend data transmitted from the controller 102 through the LAN 103 and performs a preservation processing.