PURPOSE: To provide a connecting state control system which can inform connecting state in piping passages and control connecting state in the piping passages certainly.

CONSTITUTION: An ID reader 5 provided on valve 8 side detects the identification code of an ID tag 6 provided on flexible hose 9 side. A control means 3 checks present connecting state of a piping passage 2 based on the identification code and outputs its result, and an usable piping passage constitution is selected among plural piping passage constitutions memorized in a memory means 4, when a piping passage 2 is changed by the instruction of an operator, and a connection method in order to change to a piping passage constitution which the operator desires is indicated, and moreover a connecting state after connection change of the piping passage 2 is checked based on the identification code and its result is output after collating the result with the desired piping passage constitution.