An internal combustion engine in an engine exhaust passage of which an NOx adsorption catalyst (12) adsorbing NOx contained in exhaust gas at the time of a low temperature and desorbing the adsorbed NOx when the temperature rises and an NOx storage catalyst (14) are arranged. When the NOx storage catalyst (14) can store NOx, the temperature of the NOx adsorption catalyst (12) is made to forcibly rise to a target temperature at which the amount of NOx which the NOx storage catalyst (14) can store is desorbed, and the NOx desorbed from the NOx adsorption catalyst (12) is stored in the NOx storage catalyst (14).