There is provided a configuration in which rigid substrates are connected via flexible substrates, the connection configuration having a pair of rigid substrates each having a predetermined circuit pattern on a front and a reverse surface thereof, a first flexible substrate attached on the front surfaces of the pair of the rigid substrates so as to electrically connect the circuit patterns provided respectively on the front surfaces, a second flexible substrate attached on the reverse surfaces of the pair of the rigid substrates so as to electrically connect the circuit patterns provided respectively on the reverse surfaces. The first and the second substrate have a gap therebetween smaller than a thickness of the pair of the rigid substrates.