A railway sleeper is one of the basic elements of track that directly impacts traffic safety. Railway sleepers are laid on the ballast and their purpose is to take the loads from the rails loaded with the rolling stock and to ensure the required width of the track and provide resistance to potential the vertical and horizontal shifts of the railway track system. Therefore is essential a high quality requirements for the sleepers. This thesis shortly demonstrate requirements for pre-stressed concrete railway sleeper and present production technology and the method of prestressing of sleeper B70W-60. Goal of this paper covers the numerical modelling of the sleeper and determination of immediate strain and shortening directly after prestress activation. Longitudinal shortening the sleeper immediately after releasing tension bolts, manifest itself in separating concrete from mould walls. Measuring the width of this separation is a useful indicator value – if it is too high, it may mean that there are technological process errors or an internal defect of an individual sleeper. Therefore, the numerical estimation of the separation width is a part of design process.