A vibration/noise control system controls vibrations and noises generated with a periodicity or a quasi-periodicity from a vibration/noise source having at least a rotating member. A self-expanding engine mount (2) is arranged in at least one of vibration/noise transmission paths (15) and is driven by a driving signal generated by the system. A vibration error sensor (G) detects an error signal (E) exhibiting a difference between the driving signal (Z) and the vibrations and noises. A reference sine wave is generated, which is superposed on a control signal for controlling the vibration/noise source, to thereby drive the self-expanding engine mount (2). A transfer characteristic of a portion of at least one of the vibration/noise transmission paths (15) is identified based on the reference sine wave, a delayed sine wave delayed by a predetermined delay period M relative to the reference sine wave, and the error signal (E). The transfer characteristic stored is updated based on an identification signal output from an identifying filter formed by an adaptive digital filter having two taps. The predetermined delay period M is set relative to the repetition period of the reference sine wave in a range of 1/3 ≧ M ≧ 1/7, wherein M is a real number.