An exhaust purification system comprising: an NOx occlusion reduction type catalyst that is provided in an exhaust passage of an internal combustion engine to reduce and purify NOx in an exhaust gas; a temperature acquiring unit that acquires a catalyst temperature (Temp_ LNT) of the NOx occlusion reduction type catalyst; an NOx occlusion amount estimating unit that estimates an NOx occlusion amount (M_ NOx) of the NOx occlusion reduction type catalyst; a catalyst regeneration unit that performs a catalyst regeneration process of bringing the exhaust gas into a rich state to recover NOx occlusion capacity of the NOx occlusion reduction type catalyst; a target interval setting unit (118, 119) that sets a target interval (Int_ tgr) from termination of the catalyst regeneration process by the catalyst regeneration unit to a start of a next catalyst regeneration process; a catalyst regeneration start processing unit that causes the catalyst regeneration unit to start the next catalyst regeneration process when the NOx occlusion amount (M_ NOx) estimated by the NOx occlusion amount estimating unit is equal to or greater than a predetermined threshold (NOx_ thr _ val) and an elapsed time (Int_ Time) from the termination of the catalyst regeneration process by the catalyst regeneration unit reaches the target interval (Int_ tgr); and a target interval correcting unit that corrects the target interval (Int_ tgr), wherein the target interval (Int_ tgr) is set without an interval correction when the catalyst temperature (Temp_ LNT) acquired by the temperature acquiring unit is equal to or higher than a predetermined catalyst activation temperature, and the target interval correcting unit corrects the target interval (Int_ tgr), based on the NOx occlusion amount (M_ NOx) estimated by the NOx occlusion amount estimating unit, to be longer than the target interval (Int_ tgr) that is set without the interval correction, when the catalyst temperature (Temp_ LNT) acquired by the temperature acquiring unit is lower than the predetermined catalyst activation temperature. an NOx occlusion reduction type catalyst that is provided in an exhaust passage of an internal combustion engine to reduce and purify NOx in an exhaust gas; a temperature acquiring unit that acquires a catalyst temperature (Temp_ LNT) of the NOx occlusion reduction type catalyst; an NOx occlusion amount estimating unit that estimates an NOx occlusion amount (M_ NOx) of the NOx occlusion reduction type catalyst; a catalyst regeneration unit that performs a catalyst regeneration process of bringing the exhaust gas into a rich state to recover NOx occlusion capacity of the NOx occlusion reduction type catalyst; a target interval setting unit (118, 119) that sets a target interval (Int_ tgr) from termination of the catalyst regeneration process by the catalyst regeneration unit to a start of a next catalyst regeneration process; a catalyst regeneration start processing unit that causes the catalyst regeneration unit to start the next catalyst regeneration process when the NOx occlusion amount (M_ NOx) estimated by the NOx occlusion amount estimating unit is equal to or greater than a predetermined threshold (NOx_ thr _ val) and an elapsed time (Int_ Time) from the termination of the catalyst regeneration process by the catalyst regeneration unit reaches the target interval (Int_ tgr); and a target interval correcting unit that corrects the target interval (Int_ tgr), wherein the target interval (Int_ tgr) is set without an interval correction when the catalyst temperature (Temp_ LNT) acquired by the temperature acquiring unit is equal to or higher than a predetermined catalyst activation temperature, and the target interval correcting unit corrects the target interval (Int_ tgr), based on the NOx occlusion amount (M_ NOx) estimated by the NOx occlusion amount estimating unit, to be longer than the target interval (Int_ tgr) that is set without the interval correction, when the catalyst temperature (Temp_ LNT) acquired by the temperature acquiring unit is lower than the predetermined catalyst activation temperature.