Exhaust gas purification device and exhaust purification method for an internal combustion engine

A moisture adsorbent (32) for adsorbing moisture in an exhaust gas and a NOx adsorbent (34) for adsorbing NOx are arranged (16) of an internal combustion engine (10) for bypassing an exhaust pipe in a bypass line (30). When the NOx adsorbent (34) is subjected to an adsorption, the exhaust gas is allowed to flow into the bypass line (30) until the amount of moisture that flows into the water adsorbent (32) has reached an allowable moisture. The allowable moisture is determined based on a residual amount of moisture in the moisture adsorbent (32) before the start of the adsorption operation. The residual amount of moisture in the water-adsorbent (23) can be determined based on the temperature of the moisture adsorbent (32) in the immediately preceding execution of the purge.