We present the results of our long-term photometric and spectroscopic monitoring with the1.5-m telescope RTT-150 for the optical counterpart of the high-mass X-ray binary IGR J21343+4738discovered in 2002 by the INTEGRAL space X-ray observatory. The X-ray source was also repeatedlydetected by the telescopes of the SRG observatory during the all-sky surveys in the period 2019–2021.We have investigated the spectroscopic and photometric variabilities of the optical counterpart, a Be star,caused by physical processes in the equatorial disk. We have analyzed the evolution of the equatorial diskparameters on a long time scale of 16 years.