UBV light-curves of the eclipsing binary HS Herculis, obtained in 2002-2003 observational seasons, were analysed with Wilson-Devinney computer code. New absolute dimensions of the system were calculated using the results of the light-curve analysis. Period variation of the system was also investigated. Several new times of minima have been secured for this problematic system. An apsidal motion with a period of 80.7 years was confirmed and a third body in a pretty eccentric orbit (e(3) = 0.90 +/- 0.08) with a period of 85.4 years was found. The corresponding internal structure constants of the binary system, logk(2), and the mass of the third body were derived.