The eighth SDG concerns decent working conditions. A crucial role in supporting this SDG has a sustainable business. In this article, we have considered labour demotivation in the light of the eighth SDG. We stressed the importance of improving the diagnostics system of demotivation of labour for companies that want to increase profits and be socially responsible. During the literature review, we found a lack of research on labour demotivation and diagnostics. Therefore, we analysed the diagnostic systems' composition and substantiated the main stages, criteria, and functions of the diagnostic system of labour demotivation. We also discussed the prospects of integrating demotivation diagnostics into the enterprise management system. The results of this study can be the basis for further empirical analysis of labour demotivation and can be helpful for internal HR policies improvement