An exhaust gas purification system for an internal combustion engine comprising: an NOx selective catalytic reduction catalyst that is provided in an exhaust passage of the internal combustion engine to reduce NOx in exhaust gas using ammonia as a reducing agent; urea supply means for supplying urea to said NOx selective catalytic reduction catalyst; a particulate filter that is provided in said exhaust passage to trap particulate matter in the exhaust gas; filter temperature raising means for executing a filter temperature raising control to raise the temperature of said particulate filter; and adsorbed urea quantity estimation means for estimating the quantity of urea adsorbed in said NO x selective catalytic reduction catalyst, the exhaust gas purification system being characterized in that the urea supply means, the filter temperature raising means and the adsorbed urea quantity estimation means are configured such that when the quantity of urea adsorbed in said NO x selective catalytic reduction catalyst estimated by said adsorbed urea quantity estimation means at a time when a condition for executing said filter temperature raising control is satisfied is equal to or larger than a first specific adsorption quantity, supply of urea to said NOx selective catalytic reduction catalyst by said urea supply means is stopped, and said filter temperature raising control is executed by said filter temperature raising means after a specific period of time has elapsed since the time of stoppage of supply of urea to said NOx selective catalytic reduction catalyst by said urea supply means, whereas when the quantity of urea adsorbed in said NOx selective catalytic reduction catalyst estimated by said adsorbed urea quantity estimation means at a time when a condition for executing said filter temperature raising control is satisfied is smaller than said first specific adsorption quantity, supply of urea to said NOx selective catalytic reduction catalyst by said urea supply means is not stopped, and said filter temperature raising control is executed by said filter temperature raising means. an NOx selective catalytic reduction catalyst that is provided in an exhaust passage of the internal combustion engine to reduce NOx in exhaust gas using ammonia as a reducing agent; urea supply means for supplying urea to said NOx selective catalytic reduction catalyst; a particulate filter that is provided in said exhaust passage to trap particulate matter in the exhaust gas; filter temperature raising means for executing a filter temperature raising control to raise the temperature of said particulate filter; and adsorbed urea quantity estimation means for estimating the quantity of urea adsorbed in said NO x selective catalytic reduction catalyst, the exhaust gas purification system being characterized in that the urea supply means, the filter temperature raising means and the adsorbed urea quantity estimation means are configured such that when the quantity of urea adsorbed in said NO x selective catalytic reduction catalyst estimated by said adsorbed urea quantity estimation means at a time when a condition for executing said filter temperature raising control is satisfied is equal to or larger than a first specific adsorption quantity, supply of urea to said NOx selective catalytic reduction catalyst by said urea supply means is stopped, and said filter temperature raising control is executed by said filter temperature raising means after a specific period of time has elapsed since the time of stoppage of supply of urea to said NOx selective catalytic reduction catalyst by said urea supply means, whereas when the quantity of urea adsorbed in said NOx selective catalytic reduction catalyst estimated by said adsorbed urea quantity estimation means at a time when a condition for executing said filter temperature raising control is satisfied is smaller than said first specific adsorption quantity, supply of urea to said NOx selective catalytic reduction catalyst by said urea supply means is not stopped, and said filter temperature raising control is executed by said filter temperature raising means.