The article describes a model of knowledge spreading in organizations (their departments). The model takes into account social activity of individuals and the structure of their professional knowledge. Calculations are done considering different fields of knowledge used in a group (knowledge domains, for example math, economics etc.). The model defines characteristics of knowledge spreading processes in organizations – potential coverage and routes of knowledge spreading. The model is accompanied with an example. Its advantages, disadvantages and directions for improving are determined. The model can be applied to organizational networks to estimate their potential for knowledge spreading between their agents.