An exhaust purification system for an internal combustion engine comprising: at least one selective reduction catalyst arranged in an exhaust gas passage of the exhaust purification system for the internal combustion engine and configured to reduce nitrogen compounds contained in exhaust gas with ammonia generated from an aqueous urea solution as a reducing agent for purification of the exhaust gas; aqueous urea solution injection means configured to inject the aqueous urea solution to the selective reduction catalyst; first electrical capacitance detecting means configured to detect electrical capacitance in the selective reduction catalyst, at least from a vicinity of an inlet of the selective reduction catalyst to a vicinity of a middle of the selective reduction catalyst in an exhaust gas flowing direction; second electrical capacitance detecting means configured to detect electrical capacitance in the selective reduction catalyst, at least from a vicinity of the middle of the selective reduction catalyst to a vicinity of an outlet of the selective reduction catalyst in the exhaust gas flowing direction; and reducing agent adsorption amount calculation means configured to calculate an adsorbed amount of the reducing agent in the selective reduction catalyst based on the electrical capacitance entered from the first electrical capacitance detecting means and the electrical capacitance entered from the second electrical capacitance detecting means, characterized in that the first electrical capacitance detecting means includes at least one pair of electrodes inserted into cells of the selective reduction catalyst from the inlet up to the vicinity of the middle of the selective reduction catalyst in the exhaust gas flowing direction to form a capacitor; and the second electrical capacitance detecting means includes at least one pair of electrodes inserted into cells of the selective reduction catalyst from the outlet up to the vicinity of the middle of the selective reduction catalyst along the exhaust gas flowing direction to form a capacitor, wherein at least one pair of electrodes of the first electrical capacitance detecting means and at least one pair of electrodes of the second electrical capacitance detecting means are: i) arranged in a pattern in which two rows each extending in a diametrical direction of the selective reduction catalyst are arranged in parallel; or ii) arranged in a pattern in which two sets of diametrical rows cross each other. at least one selective reduction catalyst arranged in an exhaust gas passage of the exhaust purification system for the internal combustion engine and configured to reduce nitrogen compounds contained in exhaust gas with ammonia generated from an aqueous urea solution as a reducing agent for purification of the exhaust gas; aqueous urea solution injection means configured to inject the aqueous urea solution to the selective reduction catalyst; first electrical capacitance detecting means configured to detect electrical capacitance in the selective reduction catalyst, at least from a vicinity of an inlet of the selective reduction catalyst to a vicinity of a middle of the selective reduction catalyst in an exhaust gas flowing direction; second electrical capacitance detecting means configured to detect electrical capacitance in the selective reduction catalyst, at least from a vicinity of the middle of the selective reduction catalyst to a vicinity of an outlet of the selective reduction catalyst in the exhaust gas flowing direction; and reducing agent adsorption amount calculation means configured to calculate an adsorbed amount of the reducing agent in the selective reduction catalyst based on the electrical capacitance entered from the first electrical capacitance detecting means and the electrical capacitance entered from the second electrical capacitance detecting means, characterized in that the first electrical capacitance detecting means includes at least one pair of electrodes inserted into cells of the selective reduction catalyst from the inlet up to the vicinity of the middle of the selective reduction catalyst in the exhaust gas flowing direction to form a capacitor; and the second electrical capacitance detecting means includes at least one pair of electrodes inserted into cells of the selective reduction catalyst from the outlet up to the vicinity of the middle of the selective reduction catalyst along the exhaust gas flowing direction to form a capacitor, wherein at least one pair of electrodes of the first electrical capacitance detecting means and at least one pair of electrodes of the second electrical capacitance detecting means are: i) arranged in a pattern in which two rows each extending in a diametrical direction of the selective reduction catalyst are arranged in parallel; or ii) arranged in a pattern in which two sets of diametrical rows cross each other. i) arranged in a pattern in which two rows each extending in a diametrical direction of the selective reduction catalyst are arranged in parallel; or ii) arranged in a pattern in which two sets of diametrical rows cross each other.