The exhaust purification apparatus including a control unit which estimates: a deposition amount of urea crystal in an exhaust system per unit time based on a dosing flow rate of a urea aqueous solution injected to the exhaust upstream side of a SCR converter and an exhaust gas temperature; and an accumulation amount of the urea crystal by sequentially integrating the deposition amount. The control unit further estimates: an amount of the urea crystal to be removed from the exhaust system per unit time according to the exhaust gas temperature; and an accumulation amount of the remaining urea crystal by sequentially subtracting the estimated amount, from the accumulation amount. When the accumulation amount is equal to or greater than a predetermined amount, it is determined that a timing to forcefully remove the accumulated urea crystal has arrived. Then, an alarm is activated and a forceful removing processing is performed by raising the exhaust gas temperature.