An object of the present invention is to provide a technique with which an amount of reducing agent adsorbed to a selective reduction type NOx catalyst provided in an exhaust passage of an internal combustion engine can be controlled to a target adsorption amount. In an exhaust gas purification system for an internal combustion engine according to the present invention, when a reducing agent adsorption amount adsorbed on a selective reduction type NOx catalyst is held at a target adsorption amount, a reducing agent supply amount supplied from a supply apparatus per unit time is controlled to an amount obtained by adding a predetermined amount to a reduction consumption amount, which is an amount of reducing agent consumed per unit time by the selective reduction type NOx catalyst for NOx reduction.