  We report detection of the binary companion to the millisecond pulsar
J2302+4442 based on the deep observations performed with the Gran Telescopio
Canarias. The observations revealed an optical source with $r'$ =
23.33$\pm$0.02 and $i'$=23.08$\pm$0.02, whose position coincides with the
pulsar radio position. By comparing the source colour and magnitudes with the
white dwarf cooling predictions, we found that it likely represents a He or
CO-core white dwarf and estimated its mass of 0.52$^{+0.25}_{-0.19}$
M$_{\odot}$ and effective temperature of 6300$^{+1000}_{-800}$ K. Combining our
results with the radio timing measurements, we set constraints on the binary
system inclination angle $i=73^{+6}_{-5}$ degrees and the pulsar mass
$m_p=3.1^{+2.7}_{-2.0}$ M$_{\odot}$.
