The present invention, which pertains to an exhaust purification device for an internal combustion engine, optimizes the amount of fuel supplied during forced regeneration, improving fuel economy effectively. This exhaust purification device is provided with the following: a filter (16) that is provided in an exhaust passage (12) for the internal combustion engine (10) and traps particulate matter contained in an exhaust gas; a capacitance detection unit (17a, 17b, 21) that detects the capacitance of the filter (16); and a filter regeneration unit (13, 22) that can perform forced regeneration in which fuel is supplied to the filter (16) and particulate matter that has accumulated inside the filter (16) is removed by combustion. During said forced regeneration, if the decrease per unit time of the detected capacitance falls to or below a prescribed lower threshold, indicating a decrease in the combustion efficiency of the particulate matter, the filter regeneration unit (13, 22) stops the supply of fuel.