An exhaust gas purification system comprising: an exhaust purifying element (21, 22) for purifying exhaust gas; a selective reduction catalyst for promoting reduction of NOx contained in the exhaust gas with a reducing agent; a housing for accommodating the exhaust purifying element (21, 22), wherein the housing includes a supply hole; a pipe that is located inside the housing and has a passage through which an interior of the pipe communicates with an exterior of the pipe, wherein the pipe is configured to guide exhaust gas toward the selective reduction catalyst through the passage and the interior of the pipe, and the pipe has an end communicating with the supply hole; an injection device that injects the reducing agent to an interior of the pipe through the supply hole; characterized in that the exhaust gas purification system comprises a temperature adjustment portion configured to adjust a temperature of the injection device using heating medium, wherein the housing includes an outer wall having a cylindrical accommodating portion, which is recessed into the housing, the supply hole is formed on a bottom of the accommodating portion, the injection device is coupled to the bottom of the accommodating portion outside the housing, the injection device is fastened by a fastening member to the bottom of the accommodating portion, wherein the fastening member faces an opening of the accommodating portion, and the entire fastening member is located inside the accommodating portion, the temperature adjustment portion contacts the injection device inside the accommodating portion, the temperature adjustment portion includes a pipe connector, which is coupled to a pipe guiding the heating medium, and at least a part of the pipe connector is located outside the accommodating portion. an exhaust purifying element (21, 22) for purifying exhaust gas; a selective reduction catalyst for promoting reduction of NOx contained in the exhaust gas with a reducing agent; a housing for accommodating the exhaust purifying element (21, 22), wherein the housing includes a supply hole; a pipe that is located inside the housing and has a passage through which an interior of the pipe communicates with an exterior of the pipe, wherein the pipe is configured to guide exhaust gas toward the selective reduction catalyst through the passage and the interior of the pipe, and the pipe has an end communicating with the supply hole; the pipe is configured to guide exhaust gas toward the selective reduction catalyst through the passage and the interior of the pipe, and the pipe has an end communicating with the supply hole; an injection device that injects the reducing agent to an interior of the pipe through the supply hole; characterized in that the exhaust gas purification system comprises a temperature adjustment portion configured to adjust a temperature of the injection device using heating medium, wherein the housing includes an outer wall having a cylindrical accommodating portion, which is recessed into the housing, the supply hole is formed on a bottom of the accommodating portion, the injection device is coupled to the bottom of the accommodating portion outside the housing, the injection device is fastened by a fastening member to the bottom of the accommodating portion, wherein the fastening member faces an opening of the accommodating portion, and the entire fastening member is located inside the accommodating portion, the fastening member faces an opening of the accommodating portion, and the entire fastening member is located inside the accommodating portion, the temperature adjustment portion contacts the injection device inside the accommodating portion, the temperature adjustment portion includes a pipe connector, which is coupled to a pipe guiding the heating medium, and at least a part of the pipe connector is located outside the accommodating portion.