1. A system for diagnosing a state of a construction machine in accordance with at least parameter data acquired by sensors, the system comprising: a diagnosis device for diagnosing the construction machine; a diagnostic knowledge storage device for storage of diagnostic knowledge including a diagnosing technique used for the diagnosis; and a diagnostic data storage device for storage of diagnostic data including the sensor-acquired parameter data, the diagnostic data being used for the diagnosis; wherein the diagnosis device includes: an input and output section for data input and output with respect to outside; a diagnostic data acquisition section for acquiring, on the basis of the data input to the input and output section, diagnostic data including appropriate parameter data, from the diagnostic data storage device; a data characteristics acquisition section for acquiring data characteristics of the diagnostic data acquired by the diagnostic data acquisition section, from the acquired diagnostic data, the data characteristics being inclusive of at least parameter characteristics which denote characteristics of the parameter data; a diagnostic knowledge acquisition section for acquiring, from the diagnostic knowledge storage device, any diagnosing techniques fitting the data characteristics acquired by the data characteristics acquisition section; and a diagnosing section for conducting the diagnosis using both of the diagnostic data including appropriate parameter data acquired by the diagnostic data acquisition section, and the diagnosing techniques acquired by the diagnostic knowledge acquisition section.