An electrically conductive complex obtained by reacting a thia-and/or selenafulvalenyl group-containing compound as an electron donor with an electron acceptor, and having an electron donar/electron acceptor molar ratio of 1/0.1 to 1/10, the thia-and/or selenafulvalenyl group-containing compound having the formula (I), ##STR1## wherein each of X.sub.1, X.sub.2, X.sub.3, X.sub.4, X'.sub.1, X'.sub.2, X'.sub.3 and X'.sub.4 is independently S or Se, Y is an electron donating or electron accepting group having a size which is not so large as to prevent molecular overlapping, m is an integer of 0 to 4, each of Z.sub.1, Z.sub.2, Z'.sub.1 and Z'.sub.2 is independently a hydrogen atom, C.sub.n H.sub.2n+1 in which n is an integer of 1 to 5, or alternatively, a combination of Z.sub.1 with Z.sub.2 or Z'.sub.2 and is C.sub.n H.sub.2n in which n is an integer of 1 to 5, or X(C.sub.n H.sub.2n).sub.n' X in which X is S or Se and n' is an integer of 1 to 3, and each of R.sub.1, R.sub.2, R.sub.3, R'.sub.1, R'.sub.2 and R'.sub.3 is independently a hydrogen atom or C.sub.n H.sub.2n+1 in which n is an integer of 1 to 5.