An exhaust gas purification device includes a diesel particulate filter (DPF) that traps particulate matter (PM), an exhaust gas temperature sensor that detects temperature of an exhaust gas, an electrostatic capacity detection unit that detects an electrostatic capacity of the DPF, an accumulated-amount estimation unit that estimates an amount of PM accumulated in the DPF on the basis of the electrostatic capacity, and a filter regeneration unit that can perform forced regeneration. On the basis of an accumulated-amount threshold that is lower than an upper PM accumulation limit, and a temperature threshold at which the accumulated PM can still be burned and removed even if an amount of fuel supply is reduced, the filter regeneration unit performs the forced regeneration if the amount of accumulated PM has reached the accumulated-amount threshold and the exhaust gas temperature reaches the temperature threshold.