The information recording/reproducing device includes a stacked structure which is comprised of an electrode layer and a recording layer, a buffer layer which contacts with the recording layer and a recording circuit which records data to the recording layer by generating a phase change in the recording layer. The recording layer is comprised of a complex compound having two cations, and one of the cations is a transition element having “d” orbit where electrons are incompletely filled. The recording layer is comprised of CuxAyXz (0.1≦x≦1.1, 0.9≦y≦1.1, 1.8≦z≦2.2), and includes a first chemical compound having a delafossite structure. The buffer layer is comprised of one of M3N4, M3N5, MN2, M4O7, MO2 and M2O5.