Present X-ray missions are regularly discovering new X-ray and gamma-ray sources. The identification of their counterparts at other wavelengths allows us to determine their nature. The main goal of this work is to determine the properties of the optical counterpart to the INTEGRAL source IGR J21343+4738, and to study its long-term optical variability. Although its nature as a Be/X-ray binary has been suggested, little is known about its physical parameters. We have been monitoring IGR J21343+4738 since 2009 in the optical band. We present BVRI optical photometric and spectroscopic observations covering the wavelength band 4000-7500{AA}. The photometric data allowed us to derive the colour excess E(B-V) and estimate the distance. The blue-end spectra were used to determine the spectral type of the optical companion, while the spectra around the Halpha line allowed us to study the long-term structural changes in the circumstellar disc.