The invention relates to an exhaust gas purification system and an exhaust gas purification method. This exhaust gas purification system (1, 1A) for purifying particulate matter and nitrogen oxide in exhaust gas (G) of an internal combustion engine (10) is configured with a first-stage oxidation catalyst device (21), an ammonia-based solution supply device (24), a DPF device (22), a turbine (14) of a turbo supercharger, and a selective reduction NOx catalyst device (SCR device) (23) arranged in the listed order in an exhaust system of the internal combustion engine (10), starting from the exhaust port side. With a suitable arrangement of exhaust gas purification units, the production rate of NH3 is thereby improved to improve the purification rate of NOx, the temperature of the DPF device is kept high to increase the timing and frequency of continuous regeneration, the forced regeneration of the DPF device and the amount of CO2 exhaust produced during forced regeneration are reduced, and corrosion of the turbine of the turbo supercharger by SOx is suppressed.