An exhaust purification device for an internal combustion engine is provided that can promote the reduction of NOx in a NOx purification catalyst from immediately after startup of the internal combustion engine. The exhaust purification device includes: a fuel reformer that is provided separately from exhaust plumbing 4, reforms fuel and produces a reducing gas that contains carbon monoxide, hydrogen and hydrocarbons, and supplies the reducing gas upstream of the NOx purification catalyst into the exhaust path; an exhaust gas temperature sensor 34 that detects a temperature TEX of the exhaust flowing in the exhaust plumbing 4; and a reformer control part 41 that starts supply of the reducing gas to the exhaust plumbing 4 by starting control of the fuel reformer 50 in a case where the temperature TEX thus detected by this exhaust gas temperature sensor 34 is no higher than a predetermined first determination temperature T1, and stops the supply of reducing gas to the exhaust plumbing 4 by stopping control of the fuel reformer 50 in a case where the temperature detected by the exhaust gas temperature sensor 34 is at least a second determination temperature T2, which is higher than the first determination temperature.