Bob Griffith, national secretary since the society was formed in 1986, is stepping down ahead of a six-month consultation exercise aimed at modernising the organisation's structure.
Socitm, an increasingly influential organisation in recent years, is currently taking on Microsoft about software licensing changes and the UK government on its e-government targets.
Jim Haslem, IT director at Bromley council and Socitm senior vice-president, said: "While we have an undoubted success story on our hands, the level of growth has put aspects of the society's activities and operations under strain."
Haslem also paid tribute to Griffiths, who will remain active within Socitm.
The six-month review will focus on organisational structure, including integrating the society's campaigning and commercial activities, and encouraging greater membership involvement.
Proposals will be considered at Socitm's annual general meeting in April.