In this work, the photocatalytic activity of layered GaSe flakes obtained by liquid-phase exfoliation of bulk crystals was tested on the photodegradation of an organic dye under UV irradiation. The initial bulk GaSe crystals were synthesized by stoichiometric fusion method. Investigation of the structure and composition showed that as-grown crystal corresponds to β-polytype of GaSe. Analysis of the kinetics of the decomposition MB molecules showed that the obtained flakes demonstrate good photocatalytic activity in the UV range. The efficiency of the dye photodegradation was 86% within 3 hours under UV irradiation.