An exhaust gas purification device for an engine has a filter in an engine exhaust passage, a diesel oxidation catalyst upstream of the filter, and a control unit which effects combustion using the catalyst to perform Active Regeneration of the filter by injecting fuel when no contribution is made to combustion in a combustion chamber when the quantity of particles collected in the filter reaches a predetermined quantity, or is less than the predetermined quantity and an elapsed time from the last filter reconditioning reaches a predetermined time. In the control unit, a mixing quantity of the fuel in oil at Active Regeneration and an evaporation quantity of the fuel from the oil are calculated, whereby a mixing ratio of the fuel in the oil is calculated, and the predetermined time or an engine operation mode is adjusted such that the mixing ratio does not exceed a prescribed control value.