An engine exhaust gas purification device is disclosed. The purification device has a filter (13) which traps particulate matter contained in the exhaust gas from an engine; a differential pressure detection sensor (16) which detects a differential pressure of the filter; a sensor (14, 15, 21, 31, 33) which detects an engine running state, and a microcomputer (22). The microcomputer (22) is programmed to compute an estimated ash amount ASH_a of the filter based on the detected differential pressure; compute an oil consumption amount OC_total based on the detected engine running state; compute an ash density DENS_ASH from the oil consumption amount OC_total and estimated ash amount ASH_a, and compute an ash amount ASH of the filter based on the oil consumption amount OC_total and ash density DENS_ASH.